Rockwell never called himself an artist. He routinely painted about fourteen hours a day. What I like about each of these people is that they ignored the conventions of their day, and did work that fit their vision. They also influenced others.
Every fine arts sophomore that reads too much Artforum has done a Jackson Pollock. Pollock has, IMHO, done a lot of damage to art, as he almost single-handedly created the image of the artist as a (con)artist, although Marcel Duchamp was the trailblazer.
Kincaid does one painting over and over. His light has no basis in any form of reality. I suppose it's okay, but I've never been a fan. That being said, a lot of people reject art because it looks like something that would be at a Sammi Show, but I've found that about 10% of almost any genre is great, the other 90% garbage. Like LeRoy Nieman, Kincaid as mastered the art of "Art as business for the masses." I don't think he's inherently any more dishonest than a William DeKooning or a Mark Rothko, who did the same paintings over and over, but called them a "series." The only difference, to me, is that Kincaid sells in malls, they sell in trendy galleries with white painted walls and staff dressed in black.
BTW, I missed a chance to buy a signed Norman Rockwell lithograph in 1978. It was "Shuffleton's Barber Shop." They wanted $2,000 for it then, and I was trying to put the money together when Rockwell died. The price went immediately to $10,000, well out of my range. I have no idea what it's worth now. The lithograph business is like anything else in the art world. 90% will lose value, 10% will go through the roof.
Frazetta is kind of unique. Lots of talent, ignored by the art world, I guess because of the illustrative nature of his work.
Delightful stuff, though.
http://www.frazettaartgallery.com/