Is Christianity unique or not?

[Amarok]

Viewed from 3000+ years removed, a modern perspective may see superficial similarities between ancient beliefs

What about when ancient xtians report the same similarities?

And when we say also that the Word, who is the first-birth of God, was produced without sexual union, and that He, Jesus Christ, our Teacher, was crucified and died, and rose again, and ascended into heaven, we propound nothing different from what you believe regarding those whom you esteem sons of Jupiter. For you know how many sons your esteemed writers ascribed to Jupiter: Mercury, the interpreting word and teacher of all; AEsculapius, who, though he was a great physician, was struck by a thunderbolt, and so ascended to heaven; and Bacchus too, after he had been torn limb from limb; and Hercules, when he had committed himself to the flames to escape his toils; and the sons of Leda, and Dioscuri; and Perseus, son of Danae; and Bellerophon, who, though sprung from mortals, rose to heaven on the horse Pegasus. For what shall I say of Ariadne, and those who, like her, have been declared to be set among the stars? And what of the emperors who die among yourselves, whom you deem worthy of deification, and in whose behalf you produce some one who swears he has seen the burning Caesar rise to heaven from the funeral pyre? And what kind of deeds are recorded of each of these reputed sons of Jupiter, it is needless to tell to those who already know.

Justin Martyr, c 160 AD  First Apology

Why don't you take him at his word.  After all, he was one of you.

Because they are super selective about what Christians they will believe