Before and after One More Day, many readers expressed their opinion that it would have been much better for Spider-Man to become a widower or get a divorce than to have any sort of retcon. The term often seemed to be used to describe revelations about characters that readers didn’t care for. Any new backstory that readers liked was considered to be in a different category.
It’s indicative of how terms like retcon are immediately given negative connotations, when there is nothing inherently bad (or good) about them. Retcons are simply stories which change the continuity context of previous tales. Like any storyline, a tale with a retcon has the potential to be average, mediocre or astounding, regardless of the writer, the artists, the characters, or whether or not the story exists mainly to solve a problem the editors have.
Sometimes the term is used incorrectly. Some people seem to use it as shorthand for a story they did not like. One difficulty in discussing retcons, as a concept, is that it’s a recent term, specific to serial fiction, so it hasn’t been defined by Websters, or Encarta.
Dictionary.com on the other hand has a definition…
retcon
/ret’kon/ retroactive continuity.
The common situation in fiction where a new story “reveals” things about events in previous stories, usually leaving the “facts” the same (thus preserving continuity) while completely changing their interpretation. For example, revealing that a whole season of “Dallas” was a dream was a retcon.
This term was once thought to have originated on the Usenet newsgroup rec.arts.comics but is now believed to have been used earlier in comic fandom.[The Jargon File]
In his book Writing for Comics, Peter David describes the three different types of retcons. The first is when writers tie disparate story elements together to make the mistakes seem intentional, such as Roger Stern revealing that Ned Leeds’s inability to fight the Foreigner’s goons in Amazing Spider-Man #289 was proof that Leeds wasn’t really the Hobgoblin, and had been framed. The second is when stories put modern spins on pre-existing continuity, such as John Byrne’s revelation that Lockjaw was an Inhuman. The final category of retcons is when stories establish a new and distinct continuity, sometimes with the aid of an explanation in a continuity altering event, such as The Crisis on Infinite Earths.
Jonah’s friends were wrong. As was Marv Wolfman, the guy who wrote the first parts of the story of Jonah’s nervous breakdown.
Mephisto remaking the Marvel Universe so that Peter and Mary Jane were never married would qualify as the latter sort of retcon. Had One Moment in Time established that Mephisto just mindwiped everyone in the world, it technically wouldn’t be a retcon, as everything still happened just the way it was portrayed on the page. The characters just wouldn’t remember a thing.
The assumption that any such story would be bad, predated One More Day, due to a negative perception against stories which exist to change elements of the status quo writers or editors are uncomfortable with. While a crap story can still fix the status quo and lead to better stories in the future, in which case the payoff would be worth it, there was no reason that any such story had to suck. One More Day was flawed, but that was for plenty of other reasons than the decision to opt for a magic retcon (or a mindwipe.)
Some of the best Spider-Man stories ever were created to fix problems writers had with the franchise. “Nothing Can Stop the Juggernaut” was written to get rid of Madame Web, because Roger Stern didn’t like the idea of a mysterious old psychic woman knowing Spider-Man’s identity. “The Night Gwen Stacy Died” was written because Editorial wanted something to shake up the books, while Gerry Conway thought that two ongoing storylines had gone stale: Peter Parker’s relationship with Gwen Stacy, and Spider-Man’s conflicts with the Green Goblin, which would consistently end with Norman Osborn once again forgetting his supervillain identity.
A retcon which worked in the Spider Man books was the revelation that the Hobgoblin wasn’t Ned Leeds. Some might argue that it wasn’t actually a retcon, as Roger Stern had always intended for Roderick Kingsley to be the Hobgoblin. Stern might disagree, as he admits that the story was no longer his the moment he left the title. When Peter David wrote Amazing Spider-Man #289, he intended Ned Leeds to be the Hobgoblin, and later writers built on that development. So I consider the Hobgoblin Lives to be a retcon, even if I like the story, and even if it was based on Stern’s original plans.
The Winter Solider storyline in Captain America is an obvious retcon, but it wasn’t even the most significant in that series. Hell, Bucky dying and Captain America going missing during a World War 2 mission was a retcon, contradicting all the stories in which they were alive and well and kicking communist ass in the 1950s. Those stories had their own continuity concerns, as they made it impossible for Bucky to have been fighting alongside Cap in World War Two.
While my preferred method of changing Spider-Man’s status quo would have involved retconning the revelation that Mary Jane had always known that Peter Parker was ever Spider-Man, that would have been a retcon of a retcon (Peter David refers to this as a stetcon) as that particular revelation (more on that one later) had changed the context of earlier Spider-Man stories. It has happened quite a bit in the comics.
Some might ask how a retcon differs from a previously unrevealed secret. The distinction is that a retcon contradicts prior continuity somehow. For example, Jenkins revealing details about a family tragedy for Aunt May wasn’t a retcon, because it was never established otherwise. Guggenheim’s revelation in the Character Assassination arc that Lily Hollister kissed Peter Parker in an earlier arc to distract him so that he wouldn’t discover that she was a supervillain was not a retcon, as Guggenheim was aware of that context when he wrote the scene. If Scott Snyder were to reveal in Batman that Thomas Wayne faked his death, and arranged his wife’s murder because she had cheated on him with Alfred, that would fall in the category of a retcon by contradicting previously established information in a way the original creators (and most subsequent ones) had never thought of.
What Would Spidey Do? 
I actually disagree with the notion, that the Hobgoblin retcon worked, and for the following reasons:
1) The actual three story arc, which retcons Hobgoblin continuity feels rushed, with suspects reappearing, that had not been seen in Spider-Man comics in almost a decade. So, what might have been an impactful storyline in the mid-eighties, became a sort of confusing blend of then modern day, and a decade old continuity. The revelation that a minor character from a decade earlier was the Hobgoblin ultimately felt even less impactful than the Ned Leeds reveal, which at least (despite being a red herring as Tom DeFalco stated) was build up for over a year.
2) The obvious criticism against Ned Leeds being the Hobgoblin was, that he was dispatched to easily (although I always felt there was some poetic justice in the idea of Hobgoblin screaming for Spider-Man’s help just before he died). Yet, the Hobgoblin Lives trilogy does the same with the character of Jason Macendale, who’s just thrown around like a rag doll, despite being a quite formidable enemy of Spider-Man since his latest enhancements. This was obviously done to make the real Hobgoblin seem powerful (a rather cheap plot device), but this is then again completely undone by having Spider-Man easily take out Hobgoblin with only a few punches at the end of the story.
3) It felt like really bad timing to have both the original Green Goblin and the original Hobgoblin return within a short time frame, quickly leading to Goblin overload. I personally always felt Norman Osborn was a better villain in death, than he would become in the retconned continuity. His character was completely changed from being the mentally unstable father of Peter’s best friend, who despite being a distant father, obviously loved his son (just look at ASM 98), to becoming a an all out evil manipulator, Marvel’s own Lex Luthor. Ultimately the whole character of the Hobgoblin, who was originally presented as a more more powerful, sinister, scheming, mentally stable version of the Green Goblin was sacrificed to make Norman Osborn seem super powerful.
4) Most importantly the Hobgoblin retcon completely messes up the established post-Stern continuity, as we now have to wonder, when reading those original post-Stern stories,if the character displayed is the real Hobgoblin or the Ned Leeds dupe Hobgoblin. Additionally several issues from ASM 276 onwards show the man behind the mask in the shadows with a hairline, that doesn’t match Kingsley, and all the buildup to the eventual reveal in ASM 289, despite it’s own problems, is for naught.