I only started playing the "band" type games when Guitar Hero World Tour came out. Never played anything else up until R.B., then decided to get R.B.2 just because it was a recent release, and I expected much more modern songs.
I was disappointed, probably because my expectations were higher than they should have been. The song selection was very much like any other music game, very limited. You have to UNLOCK a ton of stuff so don't plan on just going in and jamming with your friends. If you don't want to play through the career, and you want to just jam around, i would suggest another title. LOTS of downloadable content of course, but if your renting... why would you pay for all those better songs than are on the disc?
Overall, it's a fun game... character selection is fun, but lacking... songs were fun, but was lacking the modern edge... so it's just another one of those music games.... nothing special, play it if you like these games just for the experience, but don't get your expectations too high :P