Here's the thing about "One More Day": even if we assume, for the moment, that we have to end the marriage, we have to make them forget, and we have to involve Mephisto, the story still could have worked better simply be fixing the motivation to one that made sense.
As others have noted, there's something fucked up about mystically annulling your marriage to save an elderly, frail, woman who is close to death in any event.
On the other hand, if Marvel had written the story so that Peter had to do this as the only way to save MJ, his wife, it might have at least made sense. Then, you'd have Peter doing this to save the love of his life, at the cost of that love.
It's still a screwed up way to "fix" things, but at least its in character and fits with Spidey's whole notion of power and responsibility.
