Voted for Sub-Zero, but I just wanted to say that Earthworm Jim is the man. Or, the worm. Whatever. He's super strong because of his super suit, has a cool blaster that can pulverize anything it hits, and not actually having a humanoid body inside the suit would be an excellent advantage in any fight. To kill Jim you'd have to hit him, and since he's small and can duck into the suit to dodge, that'd be hard. Jim's taken down enemies of all shapes and sizes. The way his suit and his worm body interface are awesome, since he can use himself as a whip or a grappling hook or a million other ways. If he were facing anyone else, I'd be hard-pressed to find a way for him to lose.
One thing I think would happen in this fight is that Sub-Zero would freeze the suit, but miss Jim, and Jim would try and dodge. Sub-Zero could freeze the ground, making it impossible for Jim to burrow into the ground to wait for his suit to thaw. After that, it's game over for the earthworm.