So, for instance, I've been enjoying Captain America fic recently, but the fic that I'm enjoying is the sort of stuff that would never actually happen in the official story - because it's the fic where everyone is broken and is never going to get better, yet they learn to live with their brokenness and they learn to be happy, and the fic ends with the premise that everything has reached a stage of "as joyful as possible given the circumstances" and it will remain that way until all characters die of old age. Whereas, I already know that depending on what comic-book plot they follow, and, to me, all evidence points to the fact that they are going to follow this one...[Spoiler (click to open)]there's a good chance that Steve Rogers is going to die and Bucky Barnes will become Captain America. And that's not a happy ending, because someone is dead and someone must live without them.
I like things that end. Ironically, it was part of the reason I got into Supernatural - I was convinced that it would end after S5, and even if it ended in tragedy (which, at the time, Supernatural had all the markings of a clear tragedy), I would be fine with that, because at least it would have a definite end to the tragedy - and the tragedy would not continue forever. Comic books just keep going and they are ALWAYS tragic and nothing ever works out, not completely. And even if one chapter ends on a happy note, you know the next chapter is going to destroy that happiness... and I don't think I can take that when there's no clear end to the misery in sight.