Why Frank Kelly Freas was possibly the greatest science fiction artist who ever lived

Frank Kelly Freas was the best scifi artist who ever lived.
That's what I say and I'm sticking to it. There have
been illustrators who have done better aliens and more realistic
spaceships and more convincing planets and just possibly sexier heroines
(though I’m not so sure about that). But just as Frank R. Paul
was the quintessential scifi illustrator of the 20s and 30s, the art of
Kelly Freas represented—-indeed defined—-an entire era of science
fiction. Moreover, he lived and breathed science fiction. He loved the
stuff. Some of the greatest writers and editors of the half century
between 1950 and 2000 considered him a friend. Kelly was also
unflaggingly generous with his time, encouraging countless young artists
whenever he could (yours truly among them). I suspect there are
vanishingly few sci fi illustrators who grew up during the heyday of
Freas' career who were not influenced by him.