I believe that Adamantium can cut Superman.
I don't believe that Superman is dumb enough to let someone with steak-knifes coming out of his hands close enough to find out.
Superman wins 1,000,000 to every 1 Wolverine victory. And even the 1 victory comes off as unrealistic.
Wolverine wasn't able to cut the Sentry, and Sentry actually held the claws with no problem. This was years before the recent power up.
Same happened when Wolverine attacked Gladiator some years back. So as long as Superman hasn't been greatly weakened and his "bio shield" low, I don't see Wolverine as much as scratching the guy.