Packs I would buy.

[TheZellman]

Pink Floyd-
Comfortably Numb
Wish You Were Here
Money

Led Zeppelin-
Stairway to Heaven
Immigrant Song
Kashmir

Santana-
Into the Night
Smooth
Oye Como Va

Queen-
Bohemian Rhapsody
Another One Bites the Dust
Stone Cold Crazy

Tool-
The Pot
Forty Six & 2
The Grudge

The Eagles-
Hotel California
Life in the Fast Lane
Witchy Woman

Also, some stuff by Maroon 5 would fit well, but I don't know which songs I'd like best.

And then, just to make things interesting:

Bela Fleck and the Flecktones-
Oddity (no real vocals, but I'd pay to see someone scat the wind parts).

If you're not familiar with that last one, look it up and try to imagine playing it in Rock Band.

[PunishersDaddy]

I would buy almost all of those.
It would also be nice to see some blue-collar rock offerings from Springsteen, Seger and Mellencamp.

[tmanrocks]

I wouldnt buy a single one of those

I'd buy a led zeppelin pack but not that one... (Bad song choices)