In general, agricultural societies have been suggested by anthropologists to develop religions with unique characteristics, as opposed to religions in societies that live in the forest. So the Jesus religion has many of the characteristics of a typical agricultural society. It's certainly not about ancestor worship or animism. It's about a worldly king that will guide people to a promised land of milk and honey (both milk and honey come from domesticated animals primarily). So although not such a direct relationship, I think there is something legitimate to be said for the premise.On top of that, most of the "connections" touted between Jesus and certain solar deities, like Mithras and Horus, are entirely made up. If you're getting your opinions from the movie Zeitgeist, you're probably headed in the wrong direction.
It's more likely that solar-esque elements were grafted onto the Jesus narrative later, rather than the narrative deriving from previous solar worship. Jesus is compared to or connected to the sun in Biblical passages, and in Christian iconography early on, but it seems to be an original development.