From a psychological standpoint, people seem to believe in god because it gives them hope. People are afraid of death, and hate seeing injustice go unpunished. The idea that they will never have to die, and all injustice ultimately gets punished, is very appealing to them.
Also, historically, god has been brought into things a lot when science was incapable of explaining it at the time. When Newton couldn't explain why the Solar System remained stable, he decided it must have been god that did it. In the same way, when the ancients couldn't explain what the sun is, they decided it was an all-powerful light god. "God", "Magic", and similar supernatural concepts are how people make sense of things that don't make sense to them.
