Snake, destroyed giant AI robots and a nuke launching walker. in peace walker.
See, I think Snake has it's share of success too. Plus, I've seen people say that Master Chief was a perfect warrior based on the spartans or something like that; did we forget that Solid Snake is meant to be the clone of the strongest warrior in the whole world, and even defeated it! (Big Boss). He was, after all, the genetically superior brother of the ''les enfants terribles'' project; he is the ultimate warrior as much as Master chief can be, so the only real thing digging a gap between them in my opinion is sheer equipment...And even so...Snake endured inhumane punishments to complete his duties numerous times before, and survived by his tremendous will alone; let's not cast aside that he saved the world as an old man in the last MGS sequel.
I think it would depend on the situation, like if it were a gladiator fight in Rome, Chief wins, but if it's a search and destroy mission, and they need to find each-other, snake could sneak up and win.