After creating super heroes who could walk on walls, lift ten-ton weights and burst into flame, I felt the only new character who could compete with them would be some sort of god.  The god of thunder was our first choice, and one look at Lou's painting of the Mighty Thor will show you why.
                                            - Stan Lee

The Avengers were hardly your typical comic book team.  Iron Man and Thor were always at odds with the Hulk while Sub-Mariner, one of Marvel's greatest heroes, acted as a villain in the fledgling series.  Nick's illustration conveys that oddball approach which has made Marvel so unique
                                                   -  Stan Lee

Of course, there were those unforgettable times when the Avengers acted like the dedicated and daring super team they truly were.  As John's painting so clearly shows, they had more than power - they had a certain nobility about them, an inner strength, plus an unquenchable thirst for justice.
                                                           -  Stan Lee

One of the favorite recurring themes in science fiction is the determined-but-misguided scientist whose experiments take him beyond that in which mere mortals should be dabbling.  It's rare, though, that one finds a more appropriate literary venue to explore such topics than one in which your protagonist is, by definition, beyond a mere mortal.  The High Evolutionary ("High" is right; he's like Darwin on acid) aspires to godlike power, mutating animals and manufacturing his own world of Wundagore.  And, as did the Judeo/Christian deity he emulates, the Evolutionary creates his own purveyor of ultimate evil when he mutates a wolf into a slavering Man-Beast.  But despite his aspirations, he cannot control the power he's unleashed, and the Mighty Thor has to lend his own god-like abilities to the fray.  The Evolutionary would remain one of the most biblically-based characters in the Marvel Universe, engaging in scenarios reflecting both Old and New Testaments and staying juuuuust this side of good taste.
                                                  -  Peter David

Since I know this story a bit better than the others, let me just say at the outset that this is actually a picture of events that occurred in Thor #339, after Thor and Beta Ray Bill fought their epic battle.  Because of Bill's victory over Thor and the nobility he displayed in that victory, Odin granted Bill an enchanted hammer, similar to power though not in shape, to Thor's Mjolnir.  Here we see Bill holding Stormbreaker aloft for the first time into he forges of the Dwarf-fold of Eitri in Nidavellir.  But believe me, Thor and Bill fought one knockdown-dragout fight in Thor #338!  I could explain why Odin stacked the deck against his own son...but that would be telling!
                                                    -  Walter Simonson

artist: Lou Harrison
Thor versus the Midgard Serpent (Thor #380)

You'd think after as many confrontations with the Midgard (read: Earth...that is so cool!) Serpent that Thor has undoubtedly had over the centuries, everyone's favorite God of Thunder would throw up his hammer and say "Give unto me a break!  Verily, I say someone else shouldst rearrange yon serpent's dental work!"  Especially since Thor wasn't feeling particularly well at the moment this portrait was commissioned.   But nooooo...he's the first-born son of Odin of the Norse Pantheon.  So instead, he covers himself from head to toe in enchanted armor and goes about the job of kicking scale!  For the record, when the final battle between these two comes around, my money will be on the gray haired dude with the Uru walker!
                                                        -  Scott Lobdell