I have previously discussed what historians say about Jesus and history. There I used the conclusions of historians who were not arguing for or against christianity, but simply address the matter as much as possible in the same way they'd approach other aspects of ancient history.
Recently I came across an interesting analysis of the evidence from a quite different source - a Professor of Philosophy (William Lane Craig) who is a christian. He is therefore writing from a committed viewpoint, but his paper, The Evidence for Jesus, is well worth reading.
Craig considers the question of whether the gospels should be considered reliable unless proven wrong, and argues two reasons in support of this: "There was insufficient time for legendary influences to expunge the historical facts" and "The Gospel writers have a proven track record of historical reliability".