Kingdom Hearts is on the PS2.
It's put out by SqaureSoft, and one of the best selling titles on the Playstation though it was completely looked over at launch.
The premise is that the Heartless have been invading worlds. They devour people's souls, and destroy worlds. You play Sora, a boy who dreamed of leaving his world, and travelling to other worlds. You receive a keyblade, a weapon that can destroy the Heartless, and travel to a variety of words to uncover the mystery of "Kingdom Hearts".
The soundtrack is awesome, and the voice cast is the best I've ever seen assembled for a game. James Woods reprises his role as Hades, Billy Zane is the villian, Haley Joel Osmet is Sora, etc. etc.
The game mixes characters from the Final Fantasy series with Disney movies. The Nightmare Before Christmas World is the best. Gameplay is relatively unique. It's somewhat of an action RPG in a 3D world. You control the swordplay with the controller, and battles occur in real time. You can script actions for your party, and you have magic, items, and stats a plenty. The real joy of the game is the level design. Once you get to Alice in Wonderland, and see the many ways each level can be twisted and changed around, you'll be amazed. The game has tons and tons of secrets to explore.