Reflecting back on the past gives humans the ability to look objectively at themselves--the way people think, feel, and behave in different cultural circumstances. History feels so far removed from ourselves, and it becomes easier to note common themes cropping up throughout various cultures. One way to see how ancient peoples thought of themselves is to examine who they say is in charge of the cosmos. By going through such evidence as the religious writings, art, and oral histories of a people, a picture of their culture begins to appear. Not only that, but gods reflect aspects of human nature, or at least what the people considers to be human.
In some cultures, the gods represent an ideal that humans should live up to. Whether or not they can successfully emulate that ideal doesn't usually matter.
To use Christianity as an example of such a representation, Jehovah commands respect and is portrayed as powerful, infallible, pure, and good. The laws given out by Jehovah reflect how the Israelites are to behave. The Ten Commandments hold concepts such as mercy and justice in high regard, as well as respecting both their fellow man and their god. Humans are considered to be inherently evil and so cannot truly fulfil the ideal.
This differs from ancient Mesopotamian religion, in which the gods are essentially divine humans. What is meant by this, is that the gods embody human qualities and desires. There are stories filled with instances of the gods tricking one another, getting into fights, drinking contests, and the like, all behaviors associated with humans. These gods reflect culture and human nature to some extent. The Mesopotamians invented beer; it became important to everyday life in Mesopotamia, and so the gods are seen drinking it in their myths.
An example of gods reflecting human qualities appears in the Gilgamesh flood myth: Enlil wanted to sleep, but humans were incessantly noisy. In anger, Enlil devised a plan to flood the world, planning to kill mankind and start anew. Ea felt compassion for humanity and warned one man, Utnapishtim, of the impending disaster. In both cases, the gods are expressing human emotions--rage and compassion. Irritability from lack of sleep is also exceedingly human--anyone who has ever woken up has felt that at one time or another, hence all the shirts, internet memes, and blog posts saying, 'don't talk to me until my second cup of coffee.'
These two views of the cosmic order show two different aspects of human nature--a desire to have someone to look up to, and to have someone similar to you. For the Israelites, it was Jehovah, an immaculate creator. He set up rules for virtuous behavior, and the people wished to emulate his goodness For the ancient Mesopotamians, their gods were superhuman in the sense that they were exceedingly human. They were fallible, wild, and had human problems. Despite this, the people believed they had been designed to serve the gods.
Why did the people choose to follow these gods? The Mesopotamians saw something of themselves in these gods and responded accordingly.