Very interesting discussion you guys have here. I'm a theist myself.
I personally find the argument from contingency convincing.
By the way, the idea that the universe has always existed can't be right. Big Bang cosmology tells us that the universe had an absolute beginning. Scientific findings also show us that the universe is expanding, so there was a time when the universe was only a singularity.
I also believe that the default position on the question of God's existence is agnosticism. Atheists also need to give reasons why they beleive God does not exist.