The most important reason anyone is an atheist

[Sword of Christ]

I didn't assume materialism to begin with, because I was a small child who didn't know about gods. As I grew older, religious claims and god-fervor just seemed bewilderingly pointless. I never made a choice to be an atheist. Again, if you held a gun to my head and told me that I'd better believe or else, I would of course try mightily, but I'd fail, just as you would fail if you were asked to believe in Allah or Zeus. You and I are both in serious danger of Islamic hell if Muslims are right, but that idea worries neither of us.

If you're comparing God as in the eternal creator to Zeus a created being then you don't have a good understanding of what God is meant to be to begin with. Even if you want to be an atheist you need study your theology a bit first. But at least you're claiming that you choose atheism as a belief which is what it is, even if it was essentially a reaction against the fundies or whoever who are in a way determining what you believe.

What is it that you think atheists are missing in their lives that religion could give them?

A relationship with the living God? Well you already have that but an understanding/experience of it, that's the main thing you're lacking.

And why are you so determined to believe that atheism is a choice?

You said you made an active choice to be an atheist and explained why? It's a belief and you decided to adhere to it.

Now tell me what I believe and think and that I'm not a real atheist.

You seem real enough an atheist to me, I'm a good judge of these things. Though not a knowledgeable/convicted atheist if you're comparing God to Zeus.