I have always found this to be the worst argument atheists make in opposition to god. It has a simple answer in my opinion. Time, space, energy, etc., that are the cause of this god's manifestation. I know others say no time, etc... but, i will use the platform i find most logical. If these "forces" are eternal, or infinite... then, all it would take is a certain arrangement of them to manifest an incorporeal intelligence which then evolves and become something like a god.
Time and space being infinite is the platform. Energy, etc. (i say etc bc there can be other material that we aren't aware of); this arranges in such a way to create a mind. The mind is born and has been evolving and growing for eons. Therefore, all of this being the cause to this immortal consciousness and/or gods' manifestation.
I don't think it is far fetched for me to imagine such a platform since from what it looks like... there is infinite space and time. If that isn't true, then i am wrong... however, i don't think anyone can argue against it and furthermore, argue that it isn't what most likely is going on. Therefore, i think my conjecture is the best answer to who created god... time, space, energy... the infinite platforms being the cause of this "minds" manifestation. You can extend this type of logic to any god.