The following are established historical facts, according to the consensus of scholarship:
1. Jesus implicitly claimed to be God. Although the New Testament has some explicit claims along these lines, most scholars do not accept them as historical. However, they do accept that Jesus did things which, in Judaism, could only be done by God: forgiving sins, accepting worship.
2. Jesus was tortured, crucified, and killed. As N.T. Wright puts it somewhere, the crucifixion of Jesus is one of the central events in human history. You can't deny it without having to deny nearly all ancient history for consistency's sake.
3. Jesus' corpse was interred in a tomb carved out of solid rock. A large boulder weighing several tons was then lodged in the entrance to seal it. This was a common practice, and many tombs like this have been found from the same (general) area and era.
4. A couple of days after Jesus' death and burial, his tomb was found empty. One of the reasons this is widely accepted is that the New Testament presents women as the ones who discovered the empty tomb. In ancient Israel, women were considered hopeless gossips, and their testimony was considered worthless. So to say women were the ones who discovered the empty tomb could only hurt the credibility of the early Christians. The only reason to include it is because that's what actually happened, and the New Testament authors felt obligated to be honest about it.
5. "On multiple occasions and under various circumstances, different individuals and groups of people experienced appearances of Jesus alive from the dead. This is a fact that is almost universally acknowledged by New Testament scholars today." Just follow the link to read more about this.
6. The earliest Christians believed that Jesus was God incarnate, and that he literally, physically rose from the dead. These beliefs originate within days of Jesus' crucifixion and from the same place it allegedly happened (Jerusalem). They are not the product of generations of mythologizing, they were there at the very beginning.
Apart from numbers 2 and 5 (and I suspect 6, but I don't really know) there are scholars, reputable scholars, who deny these points. Nevertheless, they are accepted by the large majority of scholars and constitute the consensus positions. By "scholars" I emphatically do not mean "evangelical" scholars, or "conservative" scholars, or even "Christian" scholars. These are the consensus views by scholars across the board -- conservative and liberal, Christian and non-Christian, etc. And the scholars in question are scholars of the relevant disciplines.
None of this means that these facts are unassailable or that they cannot be questioned: of course they can. Scholars are often wrong, and the consensus of scholarship is often wrong. This is particularly the case with historical Jesus studies. I would argue, however, that the burden of proof rests on those who argue that the consensus of scholarship is wrong, or take positions entailing that the consensus of scholarship is wrong.