Well, God could also perhaps not have known. I know this may be condraticory of what the Bible says of him being an all powerful, omnicitent being, but perhaps what if he doesn't even know his power? I'm looking from Haruhi's point of view in The Melonchanly of Haruhi Shizumiya (i know i can't spell, don't rape me for it). As humans, we love the idea that we are not alone; whether it is God, Aleins, or just normal friends. Just because we can think of something doesn't make it true, but also in a sense it makes it true to the person who thought it up. Some extremeists will spend their whole life looking for proof of aliens and turn up nothing, but that won't change their view of the validity of aliens.
I guess what i'm saying is that perhaps every human, in their own way, is god. "I think therefore I am." Everyone is capable of making life and taking life, in this sense Aliens.
>_> When i went to church about 10 years ago, i always thought that The angels were Aliens.