The Elder Scrolls IV: Oblivion
Warning this game is very addictive. Think single player warcraft, but with better quests. I've been playing for 30 hours and I have barily touched the main storyline. I have been spending my time with side quests that I found interesting.
Kingdom Hearts II
Much better than the first game. I think the ability and players system is a little too complicated. But how fun is it to run around in Disney movies. I can't wait for the Tron section.
A very strange and addictive game. I can't do it justice. You just have to try it.