Traditional Christianity and Greek paganism (understanding this latter, for now, in a probably incorrect polytheistic sense) have very different understandings of God(s).
St. Augustine wrote that everything we can say of God is not true. Although far from all traditional Christian thought is apophatic, it is certainly the case that God is thought of as beyond mortal conceptions for the most part. I really don't know where people get the strange idea that Christianity believes in something like modern Theistic personalism from. If you read any of the Fathers or Divines of traditional Christianity, you find again and again that the God they are referring to is not a person or being in the sense that any created being is or could be.
Taoism, for its part, talks about the Tao, even that it calls nameless, so it isn't strictly the case that it is beyond naming. Indeed, I see certain similarities here between many traditional Christians thinkers and mystics and Taoism.
That said, I certainly wouldn't assimilate the Christian idea of God to the Tao. No two traditions ever speak about things in completely the same way. But still I think there may be interesting parallels. If Taoism is to be considered non-theistic, a designation that with due care I think is probably best, this must be separated entirely from atheism and naturalism in a modern Western sense. Taoism has infinitely more in common with traditional Christianity than with these latter.