It's so hard to decide, but...
60s: The Beatles, The Rolling Stones, CCR, The Band, Jimmy Hendrix, Cream, The Doors, Bob Dylan, Black Sabbath, Simon & Garfunkle
70s: The Rolling Stones (they’re great enough to rank twice), The Allman Brothers Band, Pink Floyd, Led Zeppelin, Cat Stevens, Elton John, ZZ Top, Eagles, Neil Young, Fleetwood Mac
80s: Dire Straits, Tom Petty, AC-DC, Bruce Springsteen, Billy Joel, The Clash, Bob Seger, Peter Gabriel, Metallica
90s: Smashing Pumpkins, Nirvana, Nine Inch Nails, Beck, Soundgarden, Pearl Jam, Oasis, Radiohead, Rage Against The Machine, R.E.M.
2000s: rock music is a joke