At the moment it's the Assassin's Creed games, particularly Brotherhood at this moment because that's the game I'm on. I blew $120 on the collector's edition with express shipping, dammit! D:
Previously it was FFX. I have well over 200 hours clocked on the game, everyone's been around almost the entire sphere grid (there's a few that I've missed for some people), and all the aeons are maxed save for Ifrit, because I can't play blitzball to save my life. I also have everyone's ultimate weapons but only Tidus, Yuna, Auron and Rikku have theirs complete. Yuna is actually stronger than Auron at this point because she's got a few more strength spheres filled in than he does. It's an odd thing to witness.