I always thought his existence was pretty much universally accepted, and the only thing open to debate was his divine nature.
Yea, it seems that his Divinity is the real key to the question.
Okay, how about this, if you live your life believing that Jesus was the actual Son of God, have you messed up your life or the afterlife? NO
However, if you become an athiest and die, then find out that Jesus really was the Son of God, you're pretty much doomed!!
Hmm, it's a pretty simple choice.