This is a question akin with the pithy saying, "Can God microwave a burrito so hot that even he can't eat it," and thus it is obvious as to why there has not been a conclusive answer without resorting to logical fallacies or ad hominem attacks. The question is ultimately unanswerable for both sides of the fence yet I find the most peculiar thing to be that both opposing philosophical teams, scientific materialism and theism, get stuck at the same point; has, "this", always been? And if not, who created, "this"? It is the same question poised in a language quipping towards the side always asking the question. Hopefully by flipping the question on its head it will be seen in the light it was meant to be seen; a question that is missing the point.
Physicists and cosmologists are stuck and no theory has given the right logical gusto to keep absolute naturalism happy. The Big Bang theory is generally accepted throughout both the science community and the common public. I remember seeing some interesting pictures of the universe a few million years right after the big bang through radio-wave imaging showing a desolate emptiness with floating gases and unstable gravitational currents. The Big Expansion should be a better analogy for the beginnings of the universe for the singularity didn't explode like an atom bomb which many people assume but the singularity of energy at the birth of the universe simply expanded and stretched its muscles to which it is still expanding today with increasing speeds. This is another question science has yet to come to a conclusive answer to. How could the universe be expanding even faster? Galaxies should be spreading out into nothingness to compensate for the loss of density over the whole universe. I do not know the answer as that I'm no scientists but it shows an interesting point to which the ones asking the ultimate question, "If God created everything, who created God", keep alluding to. What was before the big bang?
Starting from this outlook both parties are in trouble. For the theists say God is the starting point and the materialist say the big bang is the starting point yet neither side can claim what happened before. Therefore, rather than looking at this question as an attack against the religious, it should be more of a criticism of humanity's ignorance in general.
Since as stated before the question is ultimately unanswerable much like the infamous burrito question, I would like to discuss some ideas that give a bigger picture than simply, "who created God".
The Kabbala is an ancient Judaic mystical text that has been vilified by some and praised by others. There are two specific ideas that I would like to propose an objective viewing of without leaning heavily towards the religious side nor to the objectivist side. The ideas correlate with the Chinese philosophical symbol of Yin and Yang, the complementary feminine and masculine, expanding and contracting, forces of nature. Ayn is the idea of the infinite contraction or more precisely absolute nothingness and Ein sof would be the other end of the polarity meaning, "No end", or without end. If we were to entertain this idea for a moment and consider the fact that scientists are able to analyze the makeup of the Big Bang within a billionth of a second of its expansion and no more closer it can be inferred that scientists can look no more further since further would mean absolute nothingness.
The human mind cannot comprehend nothingness because there is always something. That is why black holes are so intriguing because it seems to defy our very conception of continuous somethingness (sorry for mangled language) that something without form can bend and break the very laws of nature. Therefore, I consider it best not to try to point a telescope towards Ayn because you simply will not find anything, yet on the other side of the coin scientists are pointing to the Yang of Ayn, meaning, the edge of the universe which is expanding at the speed of light. Ein Sof, is continuing its trek expanding the body of the physical universe, or the body of God in religious language, without a foreseeable end in sight.
The question of who created God should be shifted to, who is keeping this universe going? The clearest explanation seems to be one founded by man in ancient time. Ultimately that there is no beginning and there is no end in sight. What greater foundation for the endless diversity, propulsion, and velocity of nature's manifestation than nothingness as the backdrop to the grand play of life. For even the staunchest materialist must sit in awe looking at the colorful artistry of the Milky Way on a cloudless night, or the transcendent beauty of a simple flower by the roadside. From the absolute microcosm to the endless macrocosm, I do not think we can ever point directly, whether with a finger or with our mind, to the grand mechanic of it all. But in the meantime, it's fun to dance around a question that can never be answered.