I have Rock Band 3. So:

Dear Rock Band Folks,

Your musical selections are, for the most part, pretty decent. You should really have more from the 60s, but that's okay. You covered the 70s and 80s pretty well. The 90s are a little iffy, but in the interest in your monumental fuck-up regarding the next decade, I'll forgive you.

Let me just say that I respect your monumental precipice. In the last decade, a quintet of gargling yaks might have produced music with more merit than did the major labels. Still, you shouldn't have given up hope! There is some good music out there, and, yes, most of it is not major. Still, in the interest of elucidated tastes, let me propose some good material from the last ten-or-so years.

Devastation, The Besnard Lakes
All to All OR Chase Scene, Broken Social Scene
Clocks, Coldplay (COME ON, they need ONE song)
Heart Full of Pentagons, Film School
40', Franz Ferdinand (or SOMETHING by default, damnit)
Strict Machine OR Utopia OR Caravan Girl, Goldfrapp
Human, The Killers
Runaway, Ladytron
Monkey, Matthew Dear
Black Sheep, Metric
Time to Pretend, MGMT
Silvia, Miike Snow
Grace Kelly, Mika
Supermassive Black Hole, Muse
House of Cards, Radiohead
Fire With Fire OR Music is the Victim, Scissor Sisters (appropriately enough)
Photograph AND Poison, Shiny Toy Guns
Tony the Beat, The Sounds (which is just fun, okayshaddup)
Drops of Jupiter OR Meet Virginia, Train (pushing the 00s a bit)

by the way, in general, you need (some or more) U2, The Smiths, R.E.M., Paradise Lost, Lush, Led Zeppelin (STAIRWAY TO HEAVEN! and Immigrant Song, please), Garbage, Fleetwood Mac, Eurhythmics, The Eagles, CCR (by default, for Christ's sake), The Cars, The Beach Boys, Blondie