I was looking recently at a checklist I made of Scott Hampton's work, spanning close to 40 years. And I thought to myself, much as I love his work, though roughly a peer of Mignola's, who both began their comics careers in the early/mid 1980's, Mignola has a lot more star power than Scott Hampton.
I think the reason for that is because Hampton has done random work on other titles like SWAMP THING, ALIEN WORLDS, EPIC ILLUSTRATED, LEGENDS OF THE DARK KNIGHT, where he's done one-shot anthology stories or contract stories on other peoples' characters, particularly Batman.
Scott Hampton has done virtually none that could be considered signature work that he created entirely himself, that are uniquely identified with him.
SILVERHEELS is the only one that springs to mind, and that was probably created entirely by Bruce Jones, who selected Hampton to draw it.
THE UPTURNED STONE, another one-shot graphic novel, is one Hampton did completely on his own. But again, not a sustained ongoing work. Likewise several other very good one-shot anthology stories, like the PIGEONS FROM HELL Robert E. Howard adaptation, or "The Ravenant" story in TALES OF TERROR. And the stories Hampton both wrote and drew in CLIVE BARKER'S HELLRAISER 2 and 4.
Whereas in contrast, Mignola created HELLBOY which is entirely his own, and has been expanding on his creator-owned property for over 25 years. And has expanded that somewhat into a universe of titles that he is kind of the Stan Lee of. Likewise people like Robert Crumb, Jaxon, Richard Corben, and Dave Sim. Each has created a body of work that stands out as entirely their own, in a way that those who do contract work on titles arguably don't have the same visibility and distinctive identity.