Earl Norem (1923-2015) was an artist with a similar background as John Duillo. It is debatable that he is forgotten considering his comic book work is still discussed today.
Norem served in the U.S. Army 10th Mountain Division in WW II. He saw combat including getting wounded during the breakout into the Po River valley in Spring 1945.
The Earl Norem unofficial website states:
“Earl Norem has painted hundreds of memorable covers for novels, gaming books, trading cards, and Marvel Comics, bringing a fine-art style to such projeects as a SAVAGE SWORD OF CONAN, SPIDER-MAN, FANTASTIC FOUR, WIZARDS & WARRIORS, PLANET OF THE APES, MARS ATTACKS, TRANSFORMERS, MONSTERS NLEASHED, THE SIX MILLION DOLLAR MAN, and HULK. Over his five-decade career following decorated service in World War II, Norem has produced illustrations for magazines such as READERS DIGEST, FIELD AND STREAT, SKI, REAL WEST and DISCOVER, as well as movie posters for Conforte Graphics, package designs and artworld for Mego Toys, Mattel, and Hasbro, and even two New York Yankee program covers!”
He was a staple for the men’s adventure magazines of the 1950s and 60s (like John Duillo).
In the sword and sorcery realm, it is his covers for The Savage Sword of Conan for which he is remembered. If you ever looked at issues of Savage Sword on the shelves back in the day or in boxes at comic-book stores, you have seen his covers. As a friend of mine said when he died, Norem was the master of the cover of Conan, a beautiful girl in peril, and some monster. Hey, it worked.
He did some movie post art, something you probably did not know. Next to Conan, He-Man and She-Ra might his most famous character paintings.
Norem did not do much paperback art. He appears to have done all the covers for the Wizards, Warriors, & You paperbacks in the mid-1980s.
Interesting to contemplate had a publisher art director decided to use Earl Norem for 
paperback covers during the sword and sorcery boom of the late 1970s. He knew how to draw action. He was more from the comic book side of sword and sorcery than mass market paperbacks but he is still part of the history.
It’s heresy, but I prefer Earl’s “men’s adventure” work. If he had to do non-natural monsters for SSoC, I was rarely convinced by them. Still, I’m glad he found a good market.
I think Ken Barr did better S&S/fantasy work in a similar style to Norem’s. Better monsters and more intense colors.
Such passionate intensity on that Conan cover…we need more covers like that.