I gotta choose 5..
Black Sabbath - They wrote the book on metal. Everyone since owes them a paycheck or two.
Elvis Costello - Pop sensibility with caustic lyrics. If he had stopped at Armed Forces, Trust, My Aim Is True and This Years Model it would have been enough but he had to show off.
Todd Rundgren - Something, Anything... nuf said.
Earth Wind and Fire - Positivity personified wrapped inside killer grooves. Verdine was why i picked up bass..
Bowie - best front man ever and that voice.. damn