That's a good question, Ashes, and my answer would be that the default answer must indeed be that we don't know, but that it must also be probabilistic. There are simple cases where the probabilities are obvious--take a lottery, for example. If I buy a ticket, the neutral answer ahead of time must be that we don't know whether or not I'll win, but that the chances are vanishingly small.
Now, how do you assign probability to something totally abstract like God or religion? Some folks would argue you can't, and that's fine. I would use something along the lines of Solomonoff's inductive inference using Kolmogorov complexity (which sound all fancy, but together they're essentially just a formalized version of Ockham's Razor). By this model, adding a God to the universe adds an enormous quantity of complexity without actually adding any explanatory power, and so the initial probability for a God must be considered quite small. This could change with evidence one way or the other, of course. I would likely argue that over the centuries, the weight of evidence has mostly accumulated on one side and not the other, and the conception of what God is has retreated as physical evidence has failed to manifest. And I'd further argue that once you remove any possibility of physical actions from God, and make Him a sort of abstract metaphysical entity, He sort of loses His luster.
But that's neither here nor there. I'm not going to tell you you're wrong for believing, I just want to point out that it can be fair and rational to start out with a low probability for God. (Although, per the prior discussion, I'd also add that plenty of atheists are neither fair nor rational!)
Edit:
Here's a good layman's explanation of Solomonoff's induction: http://lesswrong.com/lw/dhg/an_intuitive_explanation_of_solomonoff_induction/
And now that I've read the prior page, I hope iapetus doesn't slap me!
The point being expressed is that we're dealing with guesswork. 99.9% certain people are absurdly overoptimistic about their own ability to deduce the mysteries of the universe such as in the concern with life in out of space. Sometimes, demonstrations of their poor ability to reason well, suggests to me that they are leaning on others who have far greater ability to do so. And that's kinda meh.
I find it hard to deduce how many [if any] alternate universes there are; let alone whether or not there are entities behind the universe in question. And now we have people closing the loop on the basis of absence of evidence, when in theory, everything could be evidence.
If it helps, I have faith, there are no kittens on the moon.
I mean, I don't know for sure. but I have faith.