Superman would be forced to thrash Wolverine. He'd try to reason with him, and that would either work, or he'd have to thrash him. I really think that people should start putting some thought into these set-ups and give some context.
I agree with Rasta. What reasons could you possibly give for thinking Wolverine could beat Superman? Is is because he's willing to kill? Irrelevant, considering Superman fights plenty of people who are willing to kill. Is it because he's "cooler" and has more attitude? Yeah, we all know that and that's why Wolverine is currently more popular with the younger demographic, but that doesn't overpower Superman. Is it because you don't like bright tights and a clean-shaved chin? Grow up. Superman is a god among men, and Wolverine is the best there is at what he does-- which is fight mortal foes. Wolverine can't defeat someone like Superman through force of will, because Superman's will is pretty damn strong and he has a hell of a lot of power to back it up. If there's a juvenile reason I haven't mentioned, go ahead and tell us.