There can be no question that Jesus was a real person; there are simply too many historical attestations. We have more reason to believe Jesus was a real person than Socrates, or knowledge of whom relies primarily on Plato and my namesake. Indeed, unlike in the case of Jesus Christ, where we have four independent biographies, and St. Paul and the other Apostles, in the case of Socrates we primarily have what are probably fictionalized depictions of him based primarily on Plato, contoured to suit Plato's theological, philosophical and cosmological views. And my beloved Xenophon presents Socrates in an equally hagiographic light, but does not leave us with enough information to reconstruct the "historic Socrates" beyond being able to simply say that he popularized the idea of the dialectic method and managed to (perhaps intentionally) offend the Pagan sensibilities of ancient Athens to the point of being executed.
The only historical figures we really have much biographical data on dating from their own lifetime are conquering kings and emperors, because they printed coins with their image and erected monuments to themselves. Yet most failed to make a mark of history, and even for those that did, it didn't really mean much in the end, as King Solomon realized, to his obvious dismay, and then pointed out in Ecclesiastes. No one gives more than a passing thought to King Nebuchadnezzar, or Pharoah Khufu the Pyramid Builder.
The film Cleopatra with Rex Harrison, Elizabeth Taylor and Richard Burton was mostly just epic fun, but contained one line that really stuck with me: "Yesterday, Pompey was a God."
In the case of historical people who actually matter, we have far less biographical evidence from their lives. Lao Tze, Confucius, the Buddha, Homer, Helen of Troy, the earliest of the Greek philosophers like Epimenides and Pythagoras, Zoroaster, and for that matter, Noah, Abraham, and Moses, have all been accused of being mythological. And quite possibly some of them were.
But in the case of our Lord, we have so much surviving documentation on him, some of it written within twenty years of his death, supported by so much manuscript evidence (more manuscript evidence than that in support of any other historical person, oncluding Julius Caesar, whose existence is more easily verifiable through archaeological evidence, but whose writings are much less well attested than the Gospels or Pauline epistles), that we have more reason to believe in his historicity than in that of any other ancient religious or philosophical leader preceding him, with the exception of certain individuals who were in the personal entourage of kings or emperors or other noblemen and who thus benefit from archeological attestation in the form of inscriptions and so on, for example, the high priests of the ancient Egyptian religion.