The question: "Who created God?" has a simple answer.

Mankind created all deities, using the power of minds that have evolved naturally to a degree that allows creation of concepts like that. There have been and are thousands of deities. All of them have human creators. Due to that, they can be timeless, all-knowing, all-powerful and, obviously, immortal. The minds of humans can even conceive of a deity that has always existed and requires no creator of its own.

Of course, humans created their deities in their own image. Hence, angry, vindictive deities are pretty much standard issue, although helpful, kindly deities can also be created, especially in multi-deity systems. In the case of errors in creating deities, the human mind can even edit deities to better fit a particular time frame, or introduce offsprings of deities to counter a deity that was created just a little too much like humans and that needs a more mellow counterpart. One deity can result in two, three or more deities, if need be.

That is the beauty of having humans create their own deities. A deity that becomes outmoded can be replaced by a different sort of deity, when needed. In fact, entire systems of deities can be supplanted by a single deity, if that better suits human needs. The creativity of the human mind knows no bounds. Once the new deity is in place, the obsolete ones will fade into distant memories.

Human-created deities are quite easy for other humans to believe in, since they were created by humans. They are often depicted as super humans, or wise old humans, or even as innocent infants at times. What humans create, humans can kill off, resurrect, or any other sort of thing that can be imagined. Human-created deities are able to add gravity to the rules of the culture that creates them, as well, increasing their usefulness.

That is the reason that deities seem so familiar to us. They were created by us, in our image, and so are part of us.