X-2 wins by default, as I've never played XIII or XIII-2, but I hear they're just god awful.

Unlike most people, I like FFX-2. A lot, in fact. I think it's fun and fast paced, and the mission set up of the story allows for you to play it in short intervals. The story is really, as it the overhaul of the characters...but it's FUN. I don't really look at it as a continuation of X, as it's so different, and despite being set in "Spira" is in a completely different universe.