Superman, and it's not close.
This is based on an open field, non-arena contest between a green Hulk, more or less equivalent to Ang Lee's Hulk, and a pre-Crisis Superman, more or less the movie Superman of Superman Returns. Those are my favorite versions of these characters.
Superman becomes convinced the Hulk is dangerous to Jason, Lois Lane, Jimmy Olsen or whatever. He could win easily by brute force, but prefers to fight smarter and more humanely.
Superman tunnels under the Hulk, and lifts up the island or piece of ground he's on. If the Hulk smashes through the ground and jumps toward Earth, Superman just puffs him bask on route to space anyway with superbreath and keeps going.
If the Hulk blacks out from the thin air, game over. If not, Superman just accelerates him gradually to and beyond the speed of light, and eventually lets him down lightly on some world with - functionally - sleep gas for atmosphere. Assuming the journey hasn't already bored the Hulk into becoming Bruce Banner, that does it. The Hulk being the Hulk tests the breathability of the atmosphere by breathing it, and likely keels over. But even if the Hulk just sneezes and shrugs off the gas, Superman just does something else, shifting from one humane, non-injurious tactic to another till something works.
The initiative in this fight is completely one sided, and it's an advantage to Superman that he's not an angry guy and doesn't like to beat people's faces in. Because of that, he's not going to get into a slugfest trying to break the Hulk's face and falling foul of the Hulk's growing anger, and that's the only kind of fight the Hulk can win.