Here it's a bit of the short, but excellent article:
Did ancient writers discuss the existence of Jesus?
Strikingly, there was never any debate in the ancient world about whether Jesus of Nazareth was a historical figure. In the earliest literature of the Jewish Rabbis, Jesus was denounced as the illegitimate child of Mary and a sorcerer. Among pagans, the satirist Lucian and philosopher Celsus dismissed Jesus as a scoundrel, but we know of no one in the ancient world who questioned whether Jesus lived.
How controversial is the existence of Jesus now?
In a recent book, the French philosopher Michel Onfray talks of Jesus as a mere hypothesis, his existence as an idea rather than as a historical figure. About 10 years ago, The Jesus Project was set up in the US; one of its main questions for discussion was that of whether or not Jesus existed. Some authors have even argued that Jesus of Nazareth was doubly non-existent, contending that both Jesus and Nazareth are Christian inventions. It is worth noting, though, that the two mainstream historians who have written most against these hypersceptical arguments are atheists: Maurice Casey (formerly of Nottingham University) and Bart Ehrman (University of North Carolina). They have issued stinging criticisms of the “Jesus-myth” approach, branding it pseudo-scholarship. Nevertheless, a recent survey discovered that 40% of adults in England did not believe that Jesus was a real historical figure.
This is a good intro of the issues regarding the historicity of Jesus.