Chances are if you've ever read any fantasy paperbacks published in the '60s, '70s, or '80s or merely browsed the fantasy section at a used book store, you've seen some of Frazetta
It might seem an oxymoron but, Frazetta brought a sense of realism to fantasy and science fiction art that artists like Boris Vallejo, talented tho he is, chose not to express. Frazetta painted primarily in oils, but also did watercolours and pen and ink. Later in life have suffering a mild stroke and other health problems, Frazetta taught himself to paint left handed. In 2008 his painting "Escape on Venus" sold at auction for $251,000 (US) and the following year his "Conan the Conqueror" sold for a cool $1 million. He will be missed.
If you haven't seen it, I highly recommend seeing the documentary "Frazetta: Painting with Fire" which is included on the 2-Disc edition of "Fire and Ice"
(Interesting side note, Peter Chung, later creator of Æon Flux
Unofficial Frank Frazetta Fantasy Art Gallery