Dragon said:
Why would you think that May's health, or the improvement of it would be a betrayal of her character? I think that Stan would be fine with eliminating a story telling gimmick that had long gone stale.
And honestly- what was "classic" about ASM #400? Simply that May died?
ASM #31-33 are classic because they took Spidey to his limit and showed how much inner strength he possessed.
ASM #39-40 are classic because they placed Spidey's life in jeopardy by revealing his identity to a supervillain. A scenario which would have future and tragic effect on his life.
ASM #90 was classic because it was the flipside to Amazing Fantasy #15. This time someone close to Spidey dies because he acted.
ASM #96-98 are classic because of the intertwining of a great superhero story with real-world social relevance.
ASM #121-122 are classic and I need not elaborate why.
How does ASM #400 fit in to that group? Again merely because a long established character died? In every other death of a loved one story there was more to it than merely their death. And it wasn't helped by injecting the very contrived and ridiculous revelation.
Those stories are classics because they all deal with Peter and his struggle through life, with the core themes of the character. With his determination and his devotion to becoming a responsible person--and the tragic consequences that can sometimes bring.
ASM # 400, on the other hand, deals with an external event that Peter has no control or influence over (May's revelation and subsequent death).
This has been an important and disturbing shift in Spider-Man over recent years. Now, Peter is always being acted upon by external forces, and seems like a bystander in his own books.
Whereas before (such as in the books you list above), nearly all of the events are direct results of Peter's actions or inactions.
Ben Parker died because Spider-Man chose not to act when he could have.
May Parker lived when Spider-Man summoned up the strength to free himself from tons of debris.
George Stacy died when Spider-Man failed to forsee the possible consequences of the modified web-fluid he used against Doctor Octopus.
Gwen Stacy died because Spider-Man tried to save her, but failed.
These and other stories are the result of conscious choices
Peter made, as opposed to external forces acting upon his life (the machinations of the Jackal and Norman Osborn, mystical-Totem-destiny garbage, etc.).