One of the best games I've ever played!
FFX-2 is more like a big minigame. You can fly to places whitch you've already visited in FFX (so that brings a lot of memories back) and find your old friends. Like I said, the game is also cheerier because of the music, the environment, the girls ;) and the storyline... It's also pretty hard to get a happy ending, for that you have to do surtain things like talking to Maehen in Guadosalam, get a episode clear in besaid and luca, . . . It took me like 60hours to get this (on my 3th try).
Still, this game is also pretty sad. You'll always see Yuna suffer. It's also pretty frustrating when you don't have the happy ending, you'll see Tidus in the Fareplane, like in the end of FFX he'll embrace Yuna and then disappear. . . So long story short, if you're a fan of FFX and wanna know the end, you have to buy this game, but if you're a hardcore fan of FFX, I shouldn't buy it... (I played it and I was very satisfited.)