My theory of gods is that they are mostly an egregore, which is a thought form. A psychic entity. They don't exist without worshippers but when you have believers, the belief makes it 'real' in a sense. Not that there is a physical god manifest, but instead there is the idea of god, and the idea of god drives the actions of man. So in a way a god is real if it makes you behave in accordance with the ideals of that god. The god has influence on the physical world through the believer who acts according to belief in the god. It's a self reinforcing circular subconscious manifestation of the inner workings of the mind.