Different X characters get a happy ending in almost every world. Sorata and Arashi live happily ever after in one world; Yuzuhira and Kusanagi get a happy ending in another world; Karen shows up in several worlds, once as a circus performer; and there's more, but I can't think of them all off the top of my head.

Even in the creepy horrible "X" world, at least all of the X characters are getting along and working together (by the end of the story arc) instead of trying to kill each other. Their world is post-apocalyptic, but at least it's not doomed, and there are strong hints that they'll be able to rebuild what they have left.

Oh yeah, and Subaru and Kamui make out a lot. But they're twins in that particular world, so... ew.