Rock Band 2
Guitar Hero is good, but being able to play with three other people is just so much more fun.
It's only the second time that I've been able to play a Rock Band game. I already love it. At first I did not like the idea of singing, like many I know... but something lures you in. Even if you don't know the song you can make it through using the on-screen lyrics and vocal/note guide.
I play guitar, so a lot of the guitar a bass parts feel natural, although I feel it's easier on an actual guitar. But my favorite part so far is the drums. I have a really good time on that instrument. I'm not very good at the real drums, and that's one of the great things about Rock Band (and a driving force behind the game). You can have fun playing an instrument that you're no good at. I can stay between 90-100% on a lot of songs on medium difficulty, which I'm happy with for now.
And singing, that's great too. ESPECIALLY when you DON'T know the song.

