----(think Chuck Barry, Beatles, ELO, Hall & Oates, New Wave 80's stuff, B-52s, The Cars, some pop-metal like Bon Jovi, etc.)
The Beatles are insane and expensive, but they're in talks. As for New Wave, the Police have five songs for DLC, and we're getting a Devo pack. The B-52s have a song and a promise of more to come, the Cars have AN ENTIRE DAMN ALBUM in Rock Band, which ties them for the band with the second-most songs in the game right now, and Bon Jovi have a song on the disc.
One of the biggest advantages of Rock Band is the DLC. The base setlist is nice, but on PS3 and 360 you can sign on and customize it. Love the Pixies? Buy Doolittle and rock out to Tame, Silver, and Monkey Gone to Heaven. Hate the Pixies? Skip the week and buy the rest of those Judas Priest songs you missed, or that Monkeys song from a while back, or the first Grateful Dead six pack, or the Jimmy Buffett pack. They're low on grunge and funk, but every single song that has those four instruments has a realistic chance of being DLC (as long as Aerosmith didn't write it and the masters are usable).
http://en.wikipedia.org/wiki/List_of_songs_in_rock_band#Downloadable_songs
Guitar Hero is fun, but when you're playing with three friends, scrolling through a hundred songs to construct a 3-song make a setlist and realizing that you really, really like eighty of the songs instead of just sort of having them, that's pretty awesome.