What if God were make-believe?

First thing's first, you should read the very real story that inspired this post. Please read:

http://wretchedsinner.blogspot.com/2008/11/we-lost-baby-my-3-word-response.html

I have friends who ascribe to the concept that God is great if you believe in Him, and that one way to God/heaven is as good as another. I have learned over the years the the varying concepts of God and the afterlife from the major religions and belief systems of the world are simply not logically compatible with one-another. Religion A and religion B will always contradict each other if they have any firm sense of belief structure. (Ask me about it sometime, I'm chock-full of evidence) So if they contradict each other and we're talking about God, can they possibly co-exist and be real at the same time? If God was the initial creator of time and space and claims that there is no other way to Him, as he does in the 3 major monotheistic religions, then the only logical answer is that one of them is right and the rest are wrong, or a bunch of the belief systems are right and all of the above 3 are wrong, or the Atheist favorite: none are right.

So it seems to me that there's a LOT of religious and spiritual make-believe going on, no matter how you shake it. If you tout the mantra of "whatever you want to believe is good for you, and I'll believe whatever is good for me", then you have essentially bought the make-believe concept wholesale. Here's where I get back to the linked story above: What are you going to do in the situation linked to above? How will you cope if God is only as real as you believe He is? If your faith falters, does God just fade away like the image on a dying TV screen? I really want to know folks: how do you deal with that?