There is also Jesphus, the jewish historian: http://en.wikipedia.org/wiki/Josephus_on_Jesus
But you are of course right, in that it is hard to know anything for ceratain. The whole discussion is on the basis of if it happened - then what happended? As well as what is Chrisitanity about, really?
But that is exactly what this religion - all of them, in fact - is about, isn't it? About belief. Not about facts. If there'd be a video on youtube of the whole crucifixion (or is that crucifiction) of Jesus, there most likely wouldn't be a religion based on him. Instead we might have a couple gazillion conspiracy theories.