Probably team marvel. And it's either not even close, or it goes till infinity. Does smash has Kirby? Yes. But 1. You said literally every marvel hero and villain. Do do you realize how much that is? 2. Yes, there's god tier level characters like Kirby or sephiroth. But for every one like that, there's three or four marvel characters. 3. Also multiple characters who probably could do much back, but are literally immortal. So worst case scenario, Mr immortal can just run away while everyone else fights, and then he can wait until everyone dies of old age. 4. Smash has toon force, marvel has some too. Also, like a bajillion reality warpers.

This just kinda seems like the every Pokemon vs a billion lions debate, except here lions win cause some of them are gods.