As with anything in the scientific method, the evidence must be independently reproducable and falsifiable.
Let’s start with Jesus, did he historically exist?
In all liklihood, there was an historical Jesus (or Yeshua). In fact, there were many since Yeshua was as common then as John is in the United States today.
Or was it all a myth? Yes again. As with all mythology, there is a basis in fact. My reading of the Bible leads me to believe the mythical Jesus presented in those books are a composite of several characters. Time, bandwidth, and space dictate this is neither the time nor the place to get into that discussion.