There are certainly many arguments for the existence of God -- if we're allowed to assume the world was created, you've pretty much got one right there. I think most of the arguments are valid, but they all have sufficiently dubious premises such that one is by no means required, rationally speaking, to accept them. (I.e., if you reject the comsmological argument, I don't have a prima facie case for saying you're being irrational). However, none of them will get you Christianity, except for the Ontological Argument and Pascal's Wager, and for both of those you would need a long extension of the traditional argument, making the whole thing even more dubitable.
Much of the problem hangs on the fact that Christianity is a strongly historical religion, and it's difficult to prove historical facts by means of philosophical argument. What's important to look at the evidence (and in this case, at least, it's unfair to toss out some of the evidence with the claim "We know miracles don't happen"), and decide to what extent the evidence confirms or disconfirms Christianity.
Moreover, belief isn't purely a matter of choice. So no matter how compelling the arguments, it's entirely possible to lack the emotional response that goes with what we call a "deeply held" belief. C. S. Lewis makes the point that, while they can serve to remove intellectual barriers to belief, intellectual arguments rarely, if ever, actually lead to belief in themselves.
Some links to relevant threads:
A brief discussion of the
Ontological Argument
An inconclusive discussion of the evidence for Christ's divinity is
here.