Xehanort - Ansem SoD (It's his heartless they are not different), Xemnas, Master Xehanort, Young Xehanort, Braig (Xigbar), Ias (Sai'x), and Terranort
Sora - Roxas, Ven, and Xion
Remind me if I missed any, because I'm sure I did. Anyways, yeah part of the appeal of the story at this point is to see just how stupid it can get.
Also, I liked RE: Chain of Memories, it's definitely a lot more fun, because you're no longer moving at on a 2D plain, but the game has precautions to you getting fucked on cards, it also has the best last boss music of any KH game.