If you grew up on classic fantasy art, he and Boris Vallejo were pretty much the face of the pulp fantasy cover. I had a Frazetta poster on my wall in college. The style was getting a little dated by then--it's got a 70's kinda vibe, with the swirly paint in the background, but Frazetta's compositions were so damn good and he did some very impressive stuff with color that kept it vibrant even then. And he kept putting out work, and it kept being good, for a very, very long time.
On whatever other plane artist's creations dwell, I hope he gets a Viking funeral, attended by scantily clad barbarian maidens, on a pyre pulled by polar bears.