Rock Band 2 (Xbox 360, 2008)

Pros:
Refined gameplay
Funnest song list to play on any Rhythm game yet (all Master Tracks).
Perfect instrument sound synergy.
Fail-proof mode (for beginners)
Full Multiplayer! (you don't have to be physically together to play)
Band scores on online ranking!
You can import every Rock Band 1 song for only $5!.
It lives up to It's name and reputation in every single way.

Cons:
It's exactly what it's supposed to be, don't a expect a revolution from it!
Same graphics as previous game (but they are still great!)
You still can't recreate yourself exactly in the character creation.
New drums and guitars aren't worth it if you have the old ones.

Overall thoughts:
If you liked the first one, JUST BUY IT! It's perfect and more refined! Many new options like the mutliplayer band competition, the fail proof mode that makes tough song a lot more pleasing to play if know you are going to fail in the solos (gotcha Green Grass & High Tides!), the bass solo career, the songs, the simplified band selecting options (Offline or online), and the list goes on and on... so Its just a Great game.