There are a small number of details included in the gospels, that I find more plausibly explained by there being some real Jesus rather than being entirely mythical. Why have the "superior" Jesus be baptized by the "inferior" John the Baptist? Unless there is some real memory of this Jesus being associated with John and possibly once his follower. Why have two separate stories trying to explain how he was born in Bethlehem but actually came to grow up in the areas around Galilee, unless he actually was from that area? You can also throw in a handful of statements that don't really mesh all that well with the later portrayals of Jesus.
The above material seems like living memories that they had to address rather than material one would incorporate into a developing myth.
For the record: I am inclined to think that most of the details are legends/myth. Alot of the earliest material seems to be apocalyptic in tone, with similarities to Essene ideas though. So I don't find it implausible to think there was a Jesus from Galilee influenced by this stream, and took it upon himself to spread the word. He got a little too zealous in Jerusalem though at the Temple and paid dearly for it.