The verdict of expert historians
Almost all historians believe Jesus did indeed live. The following quotes from historians who have specialised in that period of history are typical:
I don't think there's any serious historian who doubts the existence of Jesus .... We have more evidence for Jesus than we have for almost anybody from his time period.
Prof Bart Ehrman, University of North Carolina
we can no more reject Jesus' existence than we can reject the existence of a mass of pagan personages whose reality as historical figures is never questioned. ..... In recent years, 'no serious scholar has ventured to postulate the non historicity of Jesus' or at any rate very few, and they have not succeeded in disposing of the much stronger, indeed very abundant, evidence to the contrary."
The late Michael Grant, eminent historian of the Roman Empire
Jesus did exist; and we know more about him than about almost any Palestinian Jew before 70 C.E."
Prof James Charlesworth, Princeton Theological Seminary
Biblical scholars and classical historians now regard it [the theory that Jesus didn't exist] as effectively refuted."
Robert Van Voorst, Western Theological Seminary
The historical evidence for Jesus himself is extraordinarily good. .... From time to time people try to suggest that Jesus of Nazareth never existed, but virtually all historians of whatever background now agree that he did"
NT Wright
Further quotes, with sources, can be found at Quotes on Jesus as a historical person
Note: We need to be clear what the historians are saying, and not misunderstand. They are not necessarily endorsing christian belief about Jesus - some of the above historians are christians, some are not. They are simply saying that a person recognisable as the Jesus of the gospels truly lived, taught, gained a reputation as a miracle-worker and was executed - for more on what they conclude we can know about Jesus, see Jesus in history.
http://www.is-there-a-god.info/belief/wasjesusreal.shtml