I wouldn't call the evidence 100% rock solid, but I'd say the arguments for a historical Jesus are stronger than the arguments for a mythical Jesus.
* We have no eyewitness writings. But we do have second-hand writings (Paul, who spoke to and worked with Peter, who had seen him in life). No, I don't consider Paul to be a reliable witness in all (or even most) of his details, but it's a step towards support.
* We have three separate "gospel" traditions: the Synoptics, John, and Thomas. (everything else is later and derivative.)There's a lot of divergence there, so few reliable facts, but there are still some common elements that aren't likely to remain constant in a constructed myth.
* We can eliminate the "Caesar's Christ" hypothesis, because the assertions made by the Gospel are in line with Hellenized Galilean Judaism, not with Judaic Judaism, not with regular Helenistic culture, and definitely not with Roman culture. You would have had to have not just a Jew to create the myth, but a Galilean Jew. (Judean messianic claimants didn't tend to get miracle stories attributed to them: that was a pretty uniquely Galilean trait.) Josephus is off the hook: his writing style is too good to have written GoMark.
* The earliest Gospel, GoMark, is one of the most horrid examples of Greek literacy extant in First Century writing. Doesn't make for a good conspiracy.
Argumentum vox populi. I don't care how many people across the world say up is down. It ain't.