There are two sets of evidence that Christians appeal to argue that Christianity is divine rather than human in origin. First, there was the evidence of the empty tomb. The tomb, apparently, was found empty. At least, that is what the early Christians proclaimed, and it was not refuted by those people who would have wanted to see the movement quashed. The second is the fact that various people claim at least to have seen appearances of Jesus following his death. Skeptics typically respond by saying that we have reasons to have doubts about the claim that Jesus was buried in a known tomb. Executed criminals typically had their bodies dumped rather than buried. Second, skeptics typically argue that the disciples hallucinated the risen Jesus. Perhaps there weren't as many people who saw the appearances as the Bible claims. But people tend to hallucinate when they are very depressed, and are experiencing great cognitive dissonance, as must have happened to the disciples when their leader was executed on the cross. So, some people had visions, and the early Christians concluded that he must have been resurrected.
This, I think, is the best response that skeptics have to the historical case for the Resurrection. While I don't buy the hallucination story, I do think it's the strongest skeptical response.
This is still, I think the best resurrection debate, between William Lane Craig and Keith Parsons.