If god exists, and he listens to prayers and sometimes he answers them, we should suppose that he is bound by certain rules. This would be the physical rules of our world. Rules like gravity the speed of light, conservation of mass and energy, etc. So, if we make this assumption, we discover that god is not really a god but rather an omniscient kind of being, not omnipotent.
If man was created by god and we were created in his image, then god lives in a rule abiding world just like us with other beings in his likeness who may or may not be gods of their own little worlds. Which poses a theology similar to Greek theology. If this is true, then we can assume that our god was created by a god who was created by a god and so on until reaching some kind of super god, who created a single lower god or a single race of lower gods who sequentially created smaller worlds of gods until, eventually, our race will become gods of smaller worlds.
The other theory is that one of us is actually god. God is a member of the human race who doesn´t know he is god and does everything subconsciously. This god is not immortal nor is he omnipotent or omniscient. He is only bound by the laws of our world and when he dies, another god sprouts in his place and so on. This resonates with the buddhism theology.
Now, if we take the assumption that god is bound by physical rules then we find that every prayer answered must follow a set chain of events and/or reactions. If I pray for rain, god must find a cloud in the correct geological position, to make that cloud he needs to create vapor, to create vapor he needs energy, energy is neither created nor destroyed so he must transform it from somewhere, and so on. If we follow this logic then god ceases to be an omnipotent being and becomes more of an author who predicted everything long ago and created chains of events that will be followed perpetually. In this universe, god doesn´t exist anymore. He did his job and he retired.