For their body of work and impact on the industry, as opposed to simply aesthetics or scope of their portfolio, I would carve out:
Jack Kirby - creator of many Marvel heroes
Steve Ditko - creator of Spider-Man; Dr. Strange and others
Bob Kane - creator of Batman
Joe Shuster - creator of Superman
For a later era enshrinement, I'd appoint:
Frank Miller
Neal Adams
John Byrne
George Perez
...and as for current working modern artists:
I'm not sure who would truly qualify to the higher standards, possibly Jim Lee and Todd McFarlane
Hard to justify, but still not out of the question to mention Michael Turner, Marc Silvestri, J. Scott Campbell, Adam Hughes and a few other names - but those draw really petty pictures, but lack that game changing "substance" of working on memorable material more so than nice covers, splash pages and pin-ups of often times marginal characters or paired with uninspired writers.