Pretty good for something that has Disney injected into it
Kingdom Hearts 2 as with all Square RPG's, was well made, fun, and enjoyable. The main thing stopping it from getting 5 stars were a few key components that simply detracted tremendously for the game experience.
Anybody who's played the game will tell you that the beginning is perhaps one of the worst in video game history. For the first 2-3 hours, you play as a nondescript character named Roxas, going through what is essentially one long tutorial. There is little fighting, a lot of dialogue, and what's worse, Roxas disappears for the rest of the game. Confusingly, Sora somehow replaces Roxas and the game carries on as if the first few hours never happened. If the rest of the game were like this, it would've gotten 1 star.
Luckily, it's not. The rest of the game is filled with great music, lots of good fights, and diverse areas for you to explore. Graphically, there are nice sparks and waves to accompany your spells and attacks. My only complaints was that they recycled a lot of the environments from the previous game, (however, the new content mostly makes up for it), and that they story was a little convoluted.
If you look past the awkard opening, you'll get a solid RPG that can be recommended to nearly anyone.