One current rationale for the apparent fine-tuning of our universe is the multiverse theory. That is: Given an infinite number of universes, one that seems uniquely designed to support life like ours is not only possible, but inevitable.
Unfortunately, invoking an infinite number of universes we can't see to explain the one we can is essentially to invoke the supernatural. (Before you get all para-normally paranoid on me: In science, anything that is above or beyond the natural order is considered supernatural.)
This seems like a huge leap of faith. We have not observed a multiplicity of universes and we cannot empirically test them. If we are prepared to make a such a large supernatural leap of faith, why not consider a shorter, more logical jump, to a Creator?