According to the Archbishop of Canterbury, Rowan Williams, one need not believe in the Virgin Birth in order to be accounted a Christian.
During the Divine Liturgy of the Orthodox Church, the Deacon intones solemnly, before the recitation of the Creed, the Symbol of Faith, "The doors, the doors! In wisdom let us attend." The significance of this is that is a reminder of a period of Church history in which the substance of the faith was not disclosed to just anyone, as a topic of ordinary conversation, but was disclosed to the catechumens, the initiates, only gradually; as such, one could not have the congregation loudly professing their common faith in such a manner as to lay its sacred mysteries before the unbelieving world. The Creed, therefore, was so integral to the identity of the Church that she was unthinkable without it, and one could not join her unless one professed the Creed without reservation.
This, Rowan Williams effectively considers as a sort of menu, from which one may select and reject according to one's preferences. Must one also pray to Christ? May one not also pray to Buddha, or the earth-mother? Oh, wait...