The Gospels would not have been regarded as Scripture at the time they were written, so Paul would have been unlikely to quote from them in any case. He did quote from notable Gentile authors of some centuries prior nd quoted extensively from OT texts, but did not quote from any contemporary works.
It is possible (with due respect to Narkissos difference of opinion) that Jesus was a historical character (as opposed to merely historicized). When we examine the stories of George Washington or Benjamin Franklin in early U.S. lore we find ample evidence of a human tendency to romanticize key figures, especially does this trait seem to hold with poorly educated people.
Should we imagine that something similar would not have held true among poorly educated Jews? Imagine if Luke used eyewitness interviews, a recognizably suspect source, to recreate the tales of people's experiences with Ben Franklin after Ben died. Would there be some degree of accuracy? Surely. Would some of the events recorded read almost verbatim as they occurred? Yes. But, in all honesty, what else would we expect to find amongst the factual accounts?
Suppose Matthew, an eyewitness, reads Luke's account and says to himself, "Hm. Pretty accurate, but there are some bits he has happening here that actually happened here. And this bit over there is worded close to what I remember, but I distinctly recall that Jesus also said x, y, and z. And I'm sure he never said a, b, and c in my presence."
Tough to believe? Not from looking at autobiographical and biographical works of our modern times and considering how much criticism these receive by those who lived through the events described in the books.
Mark gets thrown in prison with Peter who regales him with the account from his perspective (after Peter has read the accounts of both Matthew and Luke. Mark writes an abbreviated version (who knows what the motivation is for doing so) that alters some details according to Mark's perceptions of Peter's perceptions. Will it be historically accurate? Not likely. Will it fundamentally convey Jesus as the person who told Mark the tale saw him? Very likely, whether the detail is precise or not.
John, supposedly Jesus' best friend, has the advantage of outliving most of those who could challenge his version. It's very easy to call yourself the one Christ especially loved when everyone else who knew Jesus well was already "kicked off the island" (so to speak). However, John's account gives me a more personal view of Jesus than the other Gospels, exploring more of the way Jesus felt and revealing more of the motivations for his choices than the other writers. This adds weight to the assertion that John knew him well, unless John was just a particularly gifted writer of fiction.
Actual historical figure? Yes, I believe so. Historicized? To a degree, without a doubt in my mind. However, I believe the core of the sort of person he was shines through all the clutter quite nicely. That's my take. Go ahead and tear it apart, Narkissos. I know you can.