God is the product of anthropomorphizing nature
Like many of my epiphanous revelations, this one may seem laughably obvious to many, but I tend to arrive late to the party... I am still in awe of the combustion engine, sooo....
This is more of an insight into human psychology as opposed to religion, even though it uses religious ideas as an indication as to how our minds work.
Like most of my insights, it is really quite simple: The concept of God is the product of anthropomorphizing nature..
This may not need any further explanation, but I will elaborate nevertheless.
Humans tend to project their worldview onto everything around them. The most obvious example of this is how a child, whose world is one of care, security, love, protection (or neglect, insecurity, risk, and lovelessness), will realize these same qualities on to that which he becomes attached to (through love, fear, need, etc.), such as his stuffed animal toys. How he realize these can vary greatly depending on many variables, but like most human and animal dynamics they will generally fall into a limited number of umbrella categories. Anthropomorphism is one of these vectors.
Anthropomorphism is officially described as a consequential manifestation of the mechanisms of social cognition. Social cognition is generally understood as any cognitive process that involves other people, which includes such superstructure as social knowledge, social structure, group behaviour, social influence, processing biases, whether and how social category (sex, age, race) defines people, stereotyping, memory for social information, and attribution of motives. It is a universal human quality, in that everyone does it, and a few of us are even conscious of it. According to Psychology Today it is defined as "When you talk to your dog, your computer, your teddy bear, or your car as if you were speaking to another person, you are anthropomorphizing—or attributing human characteristics like emotions and intent to a non-human entity"
I think this is a very limited definition, and in some ways completely wrong. When you speak to an animal you ARE communicating with that animal. The Animal may not know what the hell you are talking about, but it will respond in some way, even if only on a very basic stimulus-processing level, but plenty of studies have shown that communication with living things, including plants, has a measurable effect on both parties.
The anthropomorphism I am referring to is when we apply living traits to inanimate objects like a doll, or a gravestone, or a slice of toast that looks like the Virgin Mary.
It makes perfect sense why we (and abstractly speaking, perhaps all life forms) anthropomorphize objects around them. Simply put, our subjective experience of reality is how we build our worldview, which we then naturally apply to everything around us unconsciously, like a lens through which we see and interpret everything. For example, aggressive predatory hunting animals, including humans, see others as a potential threat. We can see a remnant of this in domesticated dogs who, although having lived a life of luxury, never facing any threat of any kind or the need to hunt, still are compelled to act quite aggressively towards other dogs. It would seem then that the tendency to project one's worldview into the outer world is passed on, i.e. has genetic elements to it.
As humans with the gift of self-awareness, we have the ability to be conscious of this and can understand that other people's worldview can be different than our own. This ability keeps some of us from completely destroying each other in this modern multi-cultural globalized world.
However, this is not a post about sociopolitics. This is a post about how we understand the larger reality in which we live. Our attempt to understand this greater reality is what has given rise to both the concept of God and science.
Given that science only deals with that which is measurable I am going to skip it on the premise that the greater reality in which we live is unmeasureable by current material methods. Science can tell us how to bake a cake, but it can't say anything about why we are baking a cake. The context of science is too limiting.
This is where the idea of God comes in as it provides a reason science can't. The Bible is very clear on this, and this same idea is expressed in most religious creation myths...
"Bring everyone who is called by my name, whom I created for my glory” (Isaiah 43:5–7) 
In other words, all life was created by God simply because he wanted to glorify himself. I am not saying this is a good reason, nor rational, but I'll leave this questionable motivation for another post (this is partially addressed in Abort, Retry, Fail ).
We have created a concept of that which is greater than us that id defined by our worldview that comes from our experiences and evolutionary path in the world we live in, i.e. reality as we know it. Like the child who projects his worldview onto that around him, especially that which he depends on or is attached to, we to have done the same with what we as a species depend on and what we have become attached to, which we call Nature.
Humans have been anthropomorphizing Nature in one form or another since we fall out of the trees a long time ago... or maybe even before that. We could probably reverse engineer exactly when we started to anthropomorphize nature by looking at what age children start drawing smiley faces on drawings of the sun, or when they cry when the dog chews the head of their teddy bear, and then using that age as a relative measure against social evolution. This is based in the idea that the cognitive evolution of a person mirrors the cognitive evolution of the species .
With the breakdown of the bicameral mind and the evolution of human consciousness we were able to, needed to, formalize such anthropomorphication into shared beliefs, memes, and institutions. Ergo, the stars and the planets are deities, the sun and the moon are primary gods, etc. We then apply the natural qualities of these external phenomenon to human qualities and values. Perhaps the most obvious parallel is the all-giving light of the sun, which shines equally on all, good and evil, to the all-forgiving love of God, which he bestows on all, good and evil.
We can even find examples in quantum physics which has shown that the act of observation causes a waveform to collapse into a particle, which is to say that nothing exists unless it is observed. Now, with the creation of a God, be it the Egyptian Eye of Horus, the sun-worshipping Zoroastrian's Ahura Mazda or Jehova, there is a universal observer, which justifies the existence of all reality (on a more personal level, we have Santa Claus, who is watching us 24/7 year round).
Conclusion: We have given meaning and significance to forces that have no inherent meaning or significance, based on our worldview which has an evolutionary survival need to apply meaning and pattern mainly for the purposes of prediction (how dangerous is this unknown environment? Will I eat tomorrow? Does anyone/anything want to kill/eat me?)
For the religious/spiritual reading this, you can rest well knowing that Divine Love and Forgiveness is as assured as the sun's rising and shining. For the more agnostic, carry on.
 the whole quote is "bring my sons from afar and my daughters from the end of the earth, everyone who is called by my name, whom I created for my glory, whom I formed and made.”
 This is based on Julian Jaynes theory described in his book "The Origin of Consciousness in the breakdown of the Bicameral Mind".
(sorry for the robot voice)