Read this interesting lecture about Boris Vallejo and Frank Frazetta.
They were kings of fantasy illustrations. So it's fun to debate who was better.
They share a lot of elements. Muscular barbarians fighting Monsters, Exotic animals, and naked women in chains.
But it's easy to tell the two artist apart. Boris painted shiny bodybuilders that were more staged and posing, while Frazetta's characters looked natural and grounded in their environments.
Frazetta's characters actually looked like they were in the middle of something; Boris basically did pinups. The lecturer said it best, "Boris was only as good as his models".
It's kinda cherry picking though. Sometimes Frank did more staged work, and Boris could a believable scene now and then.