Not really making too deep a point here, as I never do, but my own belief is that Jesus existed, had a life on earth, was crucified by the Romans... and then everyone who knew him discussed with lots of people who didn't what the whole point of Jesus' life had been, turning to scripture to try and find a prophetic relationship to events that they thought, or had heard, had occured. Often involving the blatant shoe horning of Jewish descriptions of ancient contempory events to a prediction of Jesus hundreds of years later.
But as we all know, when belief is involved, some very strange conclusions are very easy to reach, especially if you feel you need spiritualy or emotionally to have them... Look at Iacchus here, trying to get us all to embrace his smiley-face God, because Jesus might have suggested something 2000 years ago, or he might not... even though were the two to have ever met, as he himself admits, Jesus would have believed his view of God was different (and more accurate) to Iacchus' own... If we could send Iacchus back in time, he'd probably be known to us today as a false prophet in the Gospels, thanks to the empassioned denouncing Jesus would obviously give. Faith in Jesus was the only way to heaven, remember? So how can it be the same God they are both talking about then? And even if it is, what's this God been doing for the last 2000 years? Jesus may have existed then, but why hasn't he come back to update his words? Why isn't he here saying "look, I wanted to start out small, but these days, in a world of 6 billion, I thought I should just pop by and clarify that yes, Iacchus is talking about the same God too". Why has he left it to 2000 years of humans, and their idiocy, to warp his message so much? Why is the word of god archaic and now in so many ways errant from observable reality?
That's assuming of course that we accept God hasn't sent a new prophet for just such a reason; A number of religions, Islam being the largest, claims that he has.
The question is not so much whether Jesus existed... it's irrelevant ultimately if he did or did not. The question is; why is God's existance still in doubt...? If the answer is ultimately out there, why is it so hard to convincingly find or prove?