Right- but then we are talking about the quantity
No, we are talking about the evidence. Quality, quantity, everything. There is more evidence for a historical Jesus than there is for virtually anyone of the ancient world. Period. As you say, for those generally agreed to be historical, "more evidence" is a matter of debate. Sometimes we have less source material but simply by virtue of the improbability that fewer sources for an emperor who conquered almost the entire Near East we might have "more evidence". For Alexander the Great we have mostly later accounts that are fewer in number and are filled with legends (he is the son of a god, he is descended from Herakles, as an infant he magically reappeared and disappeared, etc.). We have statues, coins, etc., but we have these of Zeus & Herakles too. For Nero we have two lives (a form of biographical historiography, akin to the gospels, usually legendary and usually lacking the characteristic attention to or concern with chronology in ancient history, and which sought to bring out the nature of the subject through the subjects acts & deeds, including magical & legendary ones), not 4. One of them is by Suetonius, a source for Jesus, written almost a century after Nero. Another source is Tacitus, who again is a source for Jesus and actually a source for Jesus in the context of discussing Nero. For Socrates we have everything from a play to a life written some ~700 years after him and the
logoi Sokratoi, or the literary genre that Diogenes Laertius attributes to a certain Simon the Shoe-maker, if memory serves. In this genre would go the "biographical" fictions of Plato & Xenophon. For Constantine we have almost no one but Eusebius and a whole lot of fragments. For John the Baptist we have the gospels and Josephus. For the teacher of righteousness we have only the Qumran documents. For Paul, we have Paul and Acts. For Jesus' rough contemporary Apollonius of Tyana, we have only the legendary life by Philostratus, written about a century after him. For the Caesars in general, we have Suetonius as a main source and usually another life as well as many fragments and references to lost works (sometimes no different than the beginning of Luke, in which the author tells us that this work is one among many, though so far as we know the author didn't know of Matthew and Mark was the only other account of Jesus written down; this means that either the author was exaggerating, a common theme for lives as most often they were written about emperors, philosophers, and heroes, or we have other sources lost to us). In fact, for many of the lost sources we know of that supposedly mentioned various historical figures, we know of them
only through the references to these works.
for whom we have evidence from known contemporaries
That would be Jesus, for whom we have evidence from a contemporary (Paul) who knew Jesus' brother. Paul is known from his letters and Acts.
All contemporary evidence which might have existed is lost. It is referenced in what remains, but we know that such references were not always trustworthy. Also, it is hard enough at times to tell whether a work was actually written by the person claiming to be the author, let alone do this with a fragmentary quotation by e.g., Arrian or Plutarch (for whom we not only have a Pseudo-Plutarch, but who begins his "life" of Alexander with "It is agreed on by all hands, that on the father's side, Alexander
descended from Hercules by Caranus" [Ἀλέξανδρος ὅτι τῷ γένει πρὸς πατρὸς μὲν ἦν Ἡρακλείδης ἀπὸ Καράνου...τῶν πάνυ πεπιστευμένων ἐστί]).
The point being that arbitrating what ancient figures admit of more or better evidence than others can be tricky and difficult to settle, but that the evidence for Christ is on par with the evidence for other ancient figures whose historicity is generally accepted-
Fair enough.