In a post-Xmen battle between Logan and the Hulk, Hulk manages to get so angry that he breaks Wolverine's adamantium spine, killing him instantly (wikipedia.org)
I couldn't find that, but I did find reference to a fight where neither won, and the Ultimate version where Hulk ripped Wolverine in half and Wolverine survived.
Ignoring the fights that Marvel wrote already, I would say neither could win. Both the Hulk and Wolverine have been shown to have nearly unlimited healing abilities thus making a fight between the two endless.