Christianity is an amalgam of pagan religions, picking the most successful features from each.
Adonis born pre 2000 BC of virgin Astarte, for whom the spring festival of rebirth, Eastros was named, called both God the Father and Son, Crucified to save mankind and then resurrected.
Horus born 1550 BC of virgin Isis (Egyptian name for Astarte) received gifts from 3 kings, was crucified on cross, many other similarities to Jesus story.
Krishna born 1200 BC of virgin Devake, (angelic voice announced his birth to her) in a cave, (early Christian writings claimed Jesus born in cave, not manger) heralded by a bright star, while foster father in city to pay taxes, evil king Kansa tried to kill savior by ordering slaughter of all male children, visited by wise men with gifts, many sayings and teachings similar or identical to Jesus' teachings, performed many miracles and was crucified.
Indra born 725 BC of virgin, walked on water, other miracles, similar teachings, crucified-nailed to cross.
Buddha born of virgin Maya, via descent of Holy Ghost upon her, performed miracles, was crucified, went to Hades for 3 days, then ascended to Heaven.
Mithra born of virgin 600 BC, Dec 25, born in a cave, magi brought gifts, shepherds worshipped, had 12 disciples, died on cross to atone for mankind's sins, ascended to heaven at spring equinox (Eastros). Held last supper with his 12, celebrated a type of Eucharist with wafers marked with a cross.
Quirinius, born of a virgin in 506 BC, crucified by King Amulius, whole earth covered in darkness, other parallels.
Attis, born of virgin Nana 200 BC, hanged on tree, resurrected, called Father God, died as atonement of sins, followers celebrated his resurrection on Eastros by parading in streets carrying small decorated pine trees and exchanging gifts.
There are 20 crucified savior/god/resurection myths from the Middle East which predate Jesus and all incorporate several similarities found in the story of Jesus.
As you can see, early Christians incorporated the most interesting features of the above EARLIER savior-gods into a story remarkably like the one for Jesus and even appropriated the Pagan holidays and rituals. No requirement for a role model, either.
The name Jesus Christ MEANS sun-savior. Jesus is from Hebrew "Yeshua," savior, and Christ may be traced to the Chaldean "chris" = sun [Greek: christened]. The story of Christ's birth in the book of Luke is lifted from Chaldean astrology. The three wise men are the stars of Orion's belt, which rise in the east at sunset on the winter solstice. They point to the spot on the horizon where Sirius, the brightest star of all the "host of heaven" rises two hours later, and where the reborn sun rises the following morning. Other characters in the winter sky include the animals in the stable, Aries& Taurus, and the Virgin Virgo which rises at midnight, bringing forth the reborn sun.
Barbara Walker's "Woman's Encyclopedia of myths and Secrets" thoroughly documents the details of pre-Christian sun-saviors that [were mentioned].
And Abelard Reuchlin's "True Authorship of the New Testament" proposes the theory that the Christ myth was assembled by Arius Calpurnius Piso, in order to disrupt and confuse the Jewish rabbis resisting roman authority.
As you can see, there seems to be some tangible and credible support for some rather heretical (to Christians) ideas in this area. To suggest that none of these ideas was known to the writers of the Gospels is quite absurd given the time and place in which they were written. It just seems like too much of a coincidence to me that these ideas were so carefully mirrored in the story of Jesus.