Uncle DaveO is right that proving a negative is hard, but I'm not sure there is much controversy on this issue. Jewish, Christian and Muslim establishments all believe that Jesus existed. Most historians believe that he did, too. While it is true that most of the evidence comes from later, this would not be unusual of a person living in the Roman world who died at age 30. Some of the writings related to Jesus claim to be firsthand accounts, and some of those are pretty consistent with one another, so there's no reason to assume he didn't. As both Amergin and BillD pointed out, it is irrelevant in several different ways anyway :)