It's different in that it focusses on Sephiroth, and he's alive, but he's HURT. I've not seen one where he's alive, post AC, personally (though I don't look all that hard). And even if someone DID want to write him into the happily ever after, the temptation'd always be there to write him as pre-crazy, not hurt and mostly-invalid. Seeing everyone react to that: to the scary person that he was, but yet to the vulnerable person that he is now, is really cool. :)