If you are the type of person to care about such things, you may like to know that I played the first Kingdom Hearts game way back when in 2002. A little while back, I bought the second game on a whim (‘cuz I don’t play as many video games as I would like, these days).
After nearly two weeks (and about 45 hours of playtime) I’ve beaten Kingdom Hearts 2 (on easy, because the first game was surprisingly hard and I figured this one would be equally so- I was wrong). I didn’t bother with any time consuming side-quests yet, but it actually doesn’t look like there are many… I also still have a bunch of coliseum stuff to do (which I have no idea how to unlock), and Sephiroth is untouchable.
I think I liked this game more than the first one- Sora was much less annoying and the game in general was much more fun (the battles were much less stupid and tedious) but it was still a bit overly preachy, and none of the plot seemed to make any sense whatsoever. Really. Maybe you have to be Japanese, I dunno- but at least the first game was coherent. Also, less singing was involved (besides the preaching and nonsensicalness, this was clearly the most annoying part of the game- they were obviously trying to cash in on the “rhythm games” craze, but really did a shit job of it). Oh, and people familiar with the first game will be happy to know that the gummy ship levels appear to actually be fun this time around (also, highly reminiscent of the N64 Star Fox).
It was nice to see that they got rid of the Tarzan and Peter Pan type boring worlds of the first game (though I do miss Alice in Wonderland) and brought back most of the good worlds (why was the Nightmare Before Christmas board so incredibly short, though?). It was incredibly cool to play in the Tron world (Yes! Yes!); and the Timeless River (Steamboat Willy) board was pretty cool, too; but the Pirates of the Caribbean world was a bit underwhelming, IMHO. It was also really nice to be able to have a Final Fantasy character in your party for once (I think we need more Aurons and less Mulans).
Overall, I think it’s definitely worth playing if you like either Final Fantasy or Disney, or even both. If you like one and hate the other you’ll probably be fine with that, too; as the game is (like I said before) really surprisingly fun. More fun than the first one, even. Just don’t expect it to make any sense, and you’ll be fine.
Just keep in mind that while the first game was like a crossover nightmare (that happened to have a really fun story and pretty fun gameplay), this one is like you’re trapped in the 7th levell of fanfiction.net crossover hell (with a a pretty lame “We need to think of something to write- quick!” story, but incredibly fun gameplay). I fully expect the next game to be a Mary-Sue.