Music, like food, is subjective. However....
Joe Jackson> Elvis Costello
Nick Drake is one of the best artists of all time even though his three albums didn't sell shit until many years after he killed himself.
Ramsey Lewis recorded the definitive version of "Dancing in the Street".
De La Soul and Tribe Called Quest are two of the most influential rap artists.
Bruce Cockburn, although popular in Canada, is underrated everywhere else.