I think Joseph Weissman has already given one possible answer, Nietzsche. If the only Christian died on the cross, where does that leave Christianity? As myth. And not just as a Christian myth, but as already parasitical of Greek myth. Jesus is clearly acting out the part of Dionysus. The plot-scheme of the four Gospels is soaked in wine, and Jesus himself is connected with wine over and over again. Jesus acts out other parts as well (see Isaiah).
Nietzsche says God is dead, but for Nietzsche there was never a real God, the myth of God was dead. But maybe Nietzsche was too pessimistic and he didn't take into account mankind's love of a good story, but that can't be right, because he proceeded to write his own stories, his own myth!
We are dealing with myths inside of myths as the new religions dig into the past for material. Look at some of the New Age stuff. But the real possibilities of these myths (some may say stories) are in filmmaking now. Surely there will be a New Age Batman , but only after there is a Christian superhero film first. Maybe there has already been one. "Jesus Christ Superstar", (1973)?
Broadly speaking, it appears that in our history we have gone from having religions, to having myths, to having mere stories. But the relationship between religion and myth seems very complicated to me. I have read that the region of Mesopotamia was where many religions got their start. As far as religion and myth go, they seem to exist in a circular relationship with each other.
First the religion comes, then it dies or fades out, and the religion then fades into myth. The myth then becomes a source of themes and material for the making of the next religion. It's also possible for one religion to spawn another one, and Judaism has been a rich source of material in this regard. It seems that mankind needs some sort of larger-than-life narrative to keep himself going.
Over the long stretch of history, we have become thoroughly desacralized and demythologized as we have begun to "see through" the religion-myth circular interaction. We have become jaded, but we still crave the narrative. Nietzsche himself has become a source of "new"myth,Overman, Zarathustra, which is no great surprise as he had been a professor of classics, or philology, at Bern. And who is Zarathustra but Zoroaster!? Is there anything new under the sun?
Nietzsche, who supposedly wiped away metaphysics, and religion-myth created his own text or myth as a lense through which to see our world. This is the text as Derrida described it: our approach to the world is through a grand text. A massive piece of art.
But isn't this text, that tells us how "to be" just a new metaphysics? Because the largest part of a metaphysics is its ontological scheme.