New Testament scholar Larry Hurtado offers some insight on how the historical evidence for Jesus compares with the evidence of other contemporary figures:
"Part of the problem may be an insufficient acquaintance with how historians work with the limited data available. Let me illustrate this by analogous examples. To someone with limited acquaintance with ancient historical matters, it may seem impressive, for example, to learn that no writing by Jesus survives, or that a contemporary Jew such as Philo of Alexandria doesn’t mention him. So, one might buy the accusation that people posit a historical figure named Jesus without any (or adequate) basis and out of insufficiently examined bias. But, actually, the situation isn’t really so unique.
For a “pagan” example, take Apollonius of Tyana, for knowledge of whom we have almost exclusively a “Life” of the figure written by Philostratus, completed sometime in the early 3rd century CE. Per Philostratus, Apollonius lived in the early-mid first century CE, which means that our earliest text about him was composed some 150+ years after the putative date of his death. Yet, although there are many questions about exactly what he was and did, most scholars readily accept that there was such a figure. Philostratus’ “Life” is full of miraculous accounts that generate some doubts about them, and Apollonius is presented as a divine-like figure, but behind the account most scholars think there was a historical Apollonius, and that he likely had some following.
To point to Jewish examples, let’s consider Akiva, the great early rabbinic figure typically thought to have been active in the time of the Bar Kochba revolt (132-135 CE). Our earliest texts mentioning him are rabbinic writings, the earliest layer of which (Mishnah) may have been composed ca. 200 CE(?). We have anecdotes about Akiva, but large gaps in biographical information. Nevertheless, I think pretty much every scholar who has considered the matter judges that he’s a real historical figure and was of some significance.
As yet another example, let’s take Hillel, typically posited as living sometime first century BCE. He left no writings, and no contemporary mentions him (no reference in Philo, or Josephus, for example), and our earliest texts mentioning him are, again, rabbinic material, from sometime after ca. 200 CE, well over 200 years after his death. But Hillel is pretty important in Jewish tradition, and scholars (whatever their religious stance) tend to think that he lived and obviously made an impact sufficient to generate traditions about him.
You see? In positing a Jesus of Nazareth, there’s no funny business, no special pleading, no unique moves going on. It’s pretty much the same sort of historical reasoning that we have in these and other cases of ancient figures, particularly those of major significance. So, when scholars don’t react excitedly to people noting, for example, that the earliest extant narrative accounts of Jesus were written ca. 40-50 years after his death, it’s essentially because this isn’t unique. In fact, the date of the gospel accounts in relationship to the time of Jesus is comparatively pretty close. And when we note the abundant references to Jesus in Paul’s letters, dated ca. 50-60 CE (specifically, references to Jesus as born a Jew and ministering among Jews, crucified, examples of his teaching), we have even stronger basis for thinking that Jesus wasn’t some legend composed wholecloth by the gospel writers."