Doh!  We've been asking a silly question. Christianity isn't Pagan in the sense that slathering priests drink babies' blood.  Christianity is Pagan in the sense that the first Christians built their new religion out of the ideas, rituals, and myths that defined the Pagan culture they grew up in.  

Shhhh, don't tell

You're thinking of the Trilateral Commission. And it's not priests, it's bug-eyed-aliens. They also read our mail.

"Was Christianity new and unique?" What we've really been asking is, "Are our ridiculous myths different from everybody else's ridiculous myths."  The answer is No. 

I don't know about you, but now that I see it, the answer is so clear I can't believe I didn't see it before.  And the original question seems silly.  And creepy.
 

I'm not the first person to see it this way. Here's how Mrs. Crossan's little boy Johnny puts it:

Augustus came from a miraculous conception by the divine and human conjunction of [the God] Apollo and [his mother] Atia. How does the historian respond to that story? Are there any who take it literally?... That divergence raises an ethical problem for me. Either all such divine conceptions, from Alexander to Augusts and from the Christ to the Buddha, should be accepted literally and miraculously or al of them should be accepted metaphorically and theologically. It is not morally acceptable to say directly and openly that our story is truth but yours is myth; ours is history but yours is a lie. It is even less morally acceptable to say that indirectly and covertly by manufacturing defensive or protective strategies that apply only to one's own story.

John Crosssan, The Birth of Christianity, 1998, pg 28 - 29.