One More Day was the second time Marvel came close to resurrecting Gwen Stacy. As Rich Johnston noted, back when he was writing about comics gossip in his All the Rage bulletin, John Byrne and Howard Mackie had a similar idea.

On his message board, John Byrne confirmed that this was considered. It's been noted that this pitch had similarities to what eventually happened in One More Day, a similarly "cosmic" storyline. It had many flaws, and the higher‑ups at Marvel were right to reject it. First, it was odd to have an obscure character like the Shaper of Worlds have such a massive role in a major event in the Spider‑Man franchise. And this would be an oft‑reprinted book, so it could easily be the only exposure many fans have to the Shaper. I’m not even sure if any other book with the Shaper of Worlds has been reprinted.

It also takes away from the drama if there are no consequences to this magic reset button. Peter's fading memory makes the previous decades’ comic books completely irrelevant. Spider‑Man asking to return to simpler and better times echoes the opinions of the guys who came up with the idea. Byrne has expressed his belief the Spider‑Man franchise was irreparably harmed by both Peter graduating high school and the Marvel Team‑Up spinoff series, opinions he shares with Steve Ditko and Roy Thomas, making it a huge middle finger to the people who have read and enjoyed the book since then.

Peter Parker is one character who doesn’t look back at his high school days with any sense of nostalgia, so it also shows a misunderstanding of the time period, as . Hell, Peter didn't even meet Gwen until he went to college.

Changing Peter's age so obviously would also have a tremendous and probably negative impact on Marvel continuity, more so than undoing the marriage. It begs all sorts of weirder questions about the relationship between the Spider‑Man books and the rest of the Marvel Universe. How long have characters like Sandman and the Kingpin, who have had notable encounters with other Marvel superheroes, been villains? How long have the Punisher or Cloak and Dagger been active? What’s the new relationship between Spider‑Man and Daredevil or the Human Torch? The plan showed a complete ignorance of some of the things that made Marvel work, namely the shared universe.

Resurrecting Gwendy

Prior to OMD, there were some rumors that Gwen Stacy’s death would magically be undone, notably due to her role in the third Spider‑Man movie, some J Scott Campbell sketches of the character, her raised profile after the controversy over Sins Past and the correct belief that Peter and Mary Jane’s marriage will be retconned away. Joe Quesada later revealed that he had been pushing for the move. With this single change to Spider‑Man’s history, Peter might never have married Mary Jane, even if he and Gwen were to later break up. And Gwen Stacy would remain the woman who could best compete with Mary Jane for Peter Parker’s affection.

Some have asked what the difference would have been between the resurrection of the Osborns and the possible return of Gwen Stacy. The Osborns were supervillains, so resurrections are more acceptable than in the case of a character who has always been an ordinary teenage girl. With the Osborns, all of the stuff we saw in the original issues still happened. There was just other stuff we weren't privy to.

While magically retconning Spider‑Man's marriage somewhat altered several of the best regarded and significant Spider‑Man stories ever (notably Kraven's Last Hunt and the Todd Mcfarlane Venom issues) somehow preventing Gwen Stacy's death would have had more of an impact on a larger grouping of stories including Roger Stern's Hobgoblin Saga, the Harry Osborn Green Goblin Saga and the Punisher's first appearance.

Even if undoing Gwen's death was the only way to undo Sins Past (and it wouldn't even succeed in that), it would be wrong for Marvel to undo a great story with positive consequences which have affected the vast majority of the Spider‑Man comics of the last three and a half decades in order to undo a six part story and its mediocre four part sequel.

It's also wrong for the magical retcon to undo an actual death at Peter’s request, as this makes him look like a dick for not asking the Shaper of Worlds to undo other events objectively worse than the deaths of loved ones like Gwen (IE‑ any event where more than one person died) and it would beg the question of why he wouldn’t choose to undo the death of Uncle Ben (which would probably have led to Peter going to another college than ESU and never meeting Gwen or Harry Osborn), the deaths of his parents, or Dark Phoenix destroying an entire planet.

Proponents of bringing Gwen back have compared it to Ed Brubaker successfully resurrecting Bucky in Captain America. Personally, I think "The Night Gwen Stacy Died" is on a higher level than Avengers #4, in terms of its critical reputation. Bucky's death was also covered rather quickly, in a three page flashback before Captain America gets used to the modern era and helps the Avengers fight an alien. And there was never a body.

There would be slight advantages to Gwen’s return, and it would certainly muddy the waters about whether or not Peter will get back together with MJ. But it wouldn’t be worth it.

Resurrecting Gwen wouldn't bring about a long term boost in sales, and the regular public knows MJ much better than Gwen. At the same time, Gwen’s death was ultimately a positive thing for the Spider‑Man books. It was a great story, which had a significant and meaningful change to the status quo, and ultimately led to more stories than we would have gotten had Peter and Gwen Stacy just broken up.

The same wouldn’t be true of killing Aunt May or Mary Jane. Gwen’s death was so significant because it happened first. It proved that in the Marvel Universe, anything can happen. Bringing her back would be too much of a sign that nothing is permanent.

The question of whether Gwen's death should be erased was the most prominent difference between JMS's plans for One More Day, and what Marvel published.

"The Night Gwen Stacy Died" is probably the best regarded Spider-Man story ever. It's a defining point in comic book history, with some suggesting that it marked the end of the Silver Age or the beginning of the subsequent bronze age.

An article in Fantaco's 1982 Spider-Man Chronicles suggested that she was the virgin sacrifice that allowed Gerry Conway to kill off Norman Osborn. And that's sort of how she came to be viewed: the ultimate innocent. In Marvels, protagonist Phil Sheldon, a reporter for the Daily Bugle, made this explicit, as he said of the superheroes: "They weren't here to win the approval of the petty and small-minded. They were here to save the innocent. To save people like Gwen."

In "Sins Past" writer J. Michael Straczysnki retconned how Gwen had come to be seen, revealing that she was murdered because she had an affair and two children with Spider-Man's greatest enemy: the Green Goblin's alter-ego, middle-aged industrialist Norman Osborn. It was also revealed that Mary Jane had always known about this. The twins: Gabriel and Sarah Stacy, experienced a sort of accelerated aging, so they had the appearance and minds of young adults, even if chronologically, they had to be a few years younger than the likes of Billy Conners.

The story was so controversial that many expected One More Day to somehow retcon it away. It's often ranked as one of the worst Spider-Man stories ever. One guy has an extensive blog post "Redeeming Gwendy" about why he thinks it's so awful.

I don't particularly mind the revelations about Gwen, MJ or Norman. It might even have been a slight improvement from the generic girlfriend Gwen had become. As a (former) supporting character, she's allowed to mess up and/ or have bad things happen to her in ways that it can't with Peter Parker. It's the same reason Flash can lose his legs, or be an alcoholic, Harry can overdose on LSD, and even MJ can take up smoking. The suggestion in Sins Past that Peter and Gwen didn't actually have sex is an example. It bothered some readers, but I can actually buy that part of the story, as I would imagine that giving birth to twins would reduce a young woman's interest in sleeping with another guy.

I'd give the arc a "B." Mike Deodato's art is fantastic, the villains are intriguing and JMS handles the quiet moments and the emotion rather well. It ends abruptly, but the second issue in particular was exceptional.

There's still a serious flaw in the careless handling of flashbacks, especially considering how significant the revelations were. The best explanation for Gwen's behavior came from fan J.R. Fetinger AKA Madgoblin, rather than from the writer. To sum it up, there was a brief period in which Gwen Stacy thought Peter had tried to assault her elderly father. At around the same time, Norman Osborn risked his life to save hers from the Kingpin.

There were some questions about whether it was realistic for a young woman like Gwen to have a one night stand with a powerful middle-aged millionaire. It happens sometimes. It's not an impossibility.

If Peter were the father of Gwen Stacy’s children…

JMS said that his original plan was to reveal that the mystery twins were actually the children of Peter Parker, before that was vetoed by editorial. As a result, there have been questions about who was to blame for it, a discussion that's odd to participate in, as I did ultimately like the story.

Joe Quesada is to "blame" for Sins Past if he allowed JMS to make Gabriel and Sarah Stacy Peter's children when the story was in its infancy, and then reversed the decision at the last moment, when it was too late to simply go forward with a different story. If JMS had plenty of lead time and still decided to go ahead with the story of Gwen's children, he's to blame. If JMS neglected to tell Joe Quesada until the last minute that he would be introducing Peter Parker's adult children in a storyline, then he's still to blame.

During the Sins Past debacle, there were some readers who expressed their preference for Straczynski’s original plan for the storyline: that Peter Parker would be the father of Gwen Stacy’s children. They asked what the worst thing that could happen would be, and I imagined a few. On a slow news day, CNN runs the "Spider‑Man's a deadbeat dad" story. Peter Parker seems older, when he becomes the father of two kids who look like adults. Writers run out of ideas involving Peter's miraculously aged children (as there are many ideas the editors at Marvel wouldn't want the writers to explore) who are soon ignored, which further confuses readers, who don’t like it when major developments are dropped.

Possible Retcons

Some have wanted a retcon revealing that Gwen was raped. That would have resulted in new problems, especially for a series such as Amazing Spider-Man, which has a younger audience (the material is PG-13 at worse.) Aside from the obvious trauma for the victim, rape, as a crime, raises difficult questions about gender equality and sexuality. And it gets more messed up when one of the most famous Spider-Man stories is suddenly about a woman murdered by her rapist, due to a decision she made about children conceived during the rape.

While Marvel was setting up One More Day, they were also laying the seeds for the Secret Invasion crossover, which revealed that the Skrulls, a race of shape-shfting aliens, had been covertly scheming on Earth. A tie-in to that probably would have been the best way to retcon Sins Past, as it could be revealed that the Stacy twins were a Skrull plot or something. The event had not been referenced in any of Spider-Man's encounters with Norman Osborn, so at the time, so it could have been revealed a some kind of hoax in a pre-Brand New Day deck-cleaning.

Sins Past and Brand New Day

Oddly enough, Marvel's ultimate plans for One More Day and Brand New Day might have gotten in the way of any Sins Past retcon, as they now had a reason for Norman Osborn to have killed Gwen Stacy that had nothing to do with him knowing Spider-Man's identity. That was important when Norman Osborn appeared in the book, still hating Spidey but for the first time in decades, unaware of who was behind the mask.

At this point, it may be too late to put the genie back in the bottle. Sins Past has been referenced in other stories, and Gwen's children have reappeared. At some point in the future, the Spider-Man movie franchise may be relaunched with Gwen Stacy as Norman Osborn's girlfriend.

There weren't many conceivable ways for OMD to retcon Sins Past. Undoing Sins Past in One More Day would also have required a detour from that story's goal of undoing the marriage and unmasking. The story that was ultimately published dealt largely with the marriage, and tried to square the circle by keeping the stories from ASM 293-545 intact as much as possible, while changing the marital status of two characters. Whether this was successful was much-debated elsewhere.

JMS had slightly different plans for One More Day, and he thought there was a way to retcon Sins Past as well.

JMS's Recommended Retcon

JMS wanted One More Day to change Spider-Man's past in a way that prevented Gwen and Norman from having sex. Going by message board posts, many readers would have been satisfied with this solution, although if your objection to Sins Past was that it ruined Gwen's character, JMS's proposed retcon wouldn't have addressed that at all. It wouldn't have changed what's at the core of many objections to Sins Past: what the storyline said about the characters.

Gwen Stacy would still be the type of girl who might get seduced and knocked up by a friend's dad, and then keep that information from a guy she loves. Mary Jane would still keep this secret from her husband. If Gwen and Norman had children, those kids would grow at an artificially fast rate. All this would remain canon. You'd need another type of retcon to "fix" Sins Past, as you'd need something that explains her motivations or reveals somehow that it didn't happen.

I recall the majority of complaints about Sins Past being about what it did to Gwen's character, rather than the situation Gwen was placed in, although I'm sure a handful were bothered by the latter. Plus, wiping out two living beings from existence is very morally dubious.

But it would have resurrected Gwen Stacy. And it wasn't the first time the creative team of Amazing Spider-Man seriously considered that option.

Okay,
So I do not usually, and have not been following the Dark Avengers. However, there has been some recent hype about Dark Avengers # 10 with the return of Mephisto. I have not yet read it, but I believe fans are hoping to see One More Day addresses in the next issue - Dark Avengers # 11

Here is a quick summary for what happened in Dark Avengers # 10 by Combustible Pumpkins on the Spider-man reviews discussion board.

To sum it up, folks were disappearing in a small town so Norman sent the Sentry over where he mysteriously disappears. Norman arrives shortly afterward with Hammer and the rest of the DA only for them to disappear as well. Last scene Norman's in front of five or six villains who were mostly cosmically or mystically powered, one of them being Mesphito. A lot of us were hoping the OMD deal would turn out a big event to straighten out BND's continuity since it's in quite a mess now.