The setlist really is a who's who of Rock music. It covers almost all genres and is pretty well balanced. If you havent heard of the majority of the bands then I would judge that your are either extremely young or just dont listen to music.
I did not purchase the first one. I will buy a 360 just for Rock Band 2 because of great thrash bands like Testament, Megadeth, and Burton-era Metallica. Not to mention the likes of Dream Theater and Judas Priest. I played the first one a lot, but it was owned by a friend.