Rock Band 2

Rock Band 2 is pretty great. I bought the first one but wasn't really into it, but the sequel is WAY better in basically every regard. The setlist is better, the intrument controllers feel and work better, it has breakneck speed (which is a godsend for playing harder songs), and the graphics and calibration functions work better. I play both drums and guitar, though I'm way better at guitar. The fact that DLC is added about every week is pretty sweet, especially since we get some really good stuff from time to time. And the cherry on top: If you owned the first game, you can export all (except two tracks I believe) the tracks into RB2, which means that once you do that there's essentially no reason to go back to the first game.