I wouldn't bother with Guitar Hero games, but I have one question for Harmonix - where the hell is my Muse track pack, guys?. I mean, seriously..... every single one of those guys is a fantastic musician, plus their music is accessible, thereby helping to ensure you'll make quite a bit of money off such a track pack.
Out of the selection there, I picked Avenged Sevenfold for reasons which don't need explaining. Oh, and the Smashing Pumpkins need a track pack from their Gish/Mellon Collie/Siamese Dream days - Billy Corgan has written some incredible riffs in his career, and Jimmy Chamberlain is a fucking beast on the drums.