One of the best games for the PS2
It is an Action-RPG with an immersive story, easy-to-learn-hard-to-master controlling and something you just want more of.
KH2 takes place after KH1, KH: Chain of Memories and KH: 358/2 days, and even though you've only played one or none of them, you pick up the story very easily.
The story contains a mix of Disney and Final Fantasy-characters, and where some FF-fans are annoyed by the fact that some/most of the FF-characters are turned down in age, they still fit the story very well.
Besides that, the story itself is immersive from start to finish and even the middle isn't cut off. You, as Sora, travel around the world to find your friends, whom you were separated from in KH1, but finds out that the world isn't in peace. The Heartless you fought off in KH1 are still there, and new creatures called Nobodies join the fight in a battle royal. The Heartless are controlled by Maleficent from KH1 and the Nobodies are controlled by Organization XIII (where from most of the immersive of the story comes from). And as Sora, you have to fight them off.
The combat system is one of the best I've tried. It looks simple, but is at some bosses hard and struggling. Most of the enemies are easy (exception: @£$#"¤ cars!), but it's the bosses which are interesting, namely the mentioned Organization XIII. You do, however, only get to kill 6 of them in the original KH2, but they are the crown of the game. And you WILL die at them, no matter what difficulty setting you have. And you WILL do everything to kill them.
One little thing is the teammates, whom usually are idiots. But that is a minor complain, since you at the most part won't notice them and therefore not affect your gameplay. This might sound like a bad thing, but when the battles are that overwhelming, this doesn't matter a thing.
A few more "minor" things are non-linear story-progression, a good Colosseum, annoying (but funny) "The Little Mermaid"-musical and synthesis shops (Kupo!), which all gives a the beautiful glitter on a perfect cake.
Bottom line, whatever bad thing mentioned or not mentioned are quickly removed by the combat and the story. The KH-series are one of the most interesting and wanted series of the world, with a lot of fan-fiction, -screenshots, -youtube-videos, -accessories, etc.
Love it or hate it, the fans want more.
Note: I still haven't beaten Sephiroth, God Damnit!