20. Contra: Hard Corps
Set five years after Contra III (in case you were wondering where this fell in the Contra canon), Hard Corps combined all of the great, non-stop shooting gameplay with the delight of a well-made pun. Really though the appeal was simple: Contra games are great, and this had everything the previous games had PLUS 4 different characters to select from, and branching mission paths and endings, so every time you played you would have a different experience. It's a simple approach, but never doubt the Konami code (for success).
19. Comix Zone
This was one of the most unique and interesting games ever released on the Genesis you starred as Sketch, a comic artist with a horribly ironic name trapped in his own horribly named comic. The gameplay lived up to the promise of the premise though you ran and jumped through pages of the comic frame-by-frame, attacking enemies as they were being drawn in front of you. Even though it was extremely short (only 3 levels long), the game was (and probably still is) the best literal comic book game ever.
18. X-Men 2: Clone Wars
X-Men provides a lot of great fodder for videogames superpowers, villains, death being only a temporary deterrent but there was always a problem with videogame adaptations: they limited how often you could use your powers. Cyclops wants to use Optic Blast? Well he only gets to do it a few times. The rest of time you have to do lame kicks and punches like an unpowered loser who can't shoot laser beams out of his eyeballs. Clone Wars changed that now you could use your powers as often as you wanted (with a nice roster including Cyclops, Wolverine, and Magneto in his first playable videogame appearance), albeit if you wanted to use them well, you had to charge them up. A small price to pay for the best non-6-player-arcade X-Men game.
17. Altered Beast
Of all the games about undead ancient Greece zombie heroes, Altered Beast is probably among the best. Side scrolling through graveyards and the underworld was made all the better by being able to transform into a werewolf, weredragon (who can shoot lightning bolts out of his eyes), weretiger, and a werebear, which is just as badass as it is hilarious to say aloud. Plus, the majority of the game is spent kicking zombies in the groin until they explode. The game feels a little rusty these days, but it still holds up as one of the finest platformers around. Also: WEREDRAGON.
16. Toejam and Earl
There's never been another game quite like the original Toejam and Earl. How many games do you spend all your time casually strolling around and opening presents? The genius of taking the two chillest aliens possible and giving them a relaxing stroll through a series of floating blobs of land is that when something horrifying showed up the present moles, swarms of bees, or sharks it became more terrifying than almost anything in any other game. It was like a terrifying Christmas morning every time you played the game. Although hopefully no one ever gave you "instant death" as a present.