I didn't much appreciate fighting Xemnas in Kingdom Hearts 2. See, in the first game, you're fighting 'Ansem' (cough cough) and it gets really tough, I struggled for ages trying to get past the stage where you're in that little bowl area and Donald/Goofy are trapped outside on the beach. Then in KH2, you reach Xemnas, and he's piss easy. There's still several stages, and it's still pretty damn cool (like the bit where you fight on the back of a mother-fucking dragon...), but it's still too easy to be worth all that trouble in the rest of the game.
Though it was still a good game. Any game where you fight a thousand Heartless at once just has to be good...