Kind of fun to think about it... I'll post mine

ABBA: ***
The Beach Boys: ****
The Beatles: *****
Black Sabbath: ***
Brand X: ***
David Bowie: ****
Cream: ***
Eric Clapton (including Derek and the Dominos): ****
Coldplay: ***
Death: ***
Deep Purple: ****
Dire Straits: ***
Dream Theater: ***
Bob Dylan: ***
Electric Light Orchestra: ***
Emerson, Lake and Palmer: ****
Faith No More: ****
The Flaming Lips: ***
Peter Gabriel: ****
Genesis: *****
Jethro Tull: ****
King Crimson: *****
Led Zeppelin: ***
Megadeth: ***
Metallica: ****
The Moody Blues: ***
Nirvana: ***
Radiohead: *****
The Rolling Stones: *****
Steely Dan: ****
Van Der Graaf Generator: ****
Van Halen: **
The Velvet Underground: ***
Ween: ****
The Who: *****
Frank Zappa: ***