The God myth or idea comes from the unconscious it is a projection just like the colors we see are a projection. It is also according to Jungian Psychology an archetype, such as gods and goddesses are.
It is the way the unconscious(the upper layer that is sometimes accessible to ego consciousness) organizes it self and the bases for our interpretation or experiencing of the world,, with ready made responses or instincts.
The ultimate God of everything can never be proven or dis-proven as both are an impossibility. But when speak of this Ultimate Being, psychically it can be classified as an Archetype, often referred to as the "Self". It can be experienced as the center of the human psyche and is supposed to be the most real and life changing of experiences one can have, not to mention scary and a whole gamut of very strong feeling toned sensations,, more so than any of the other archetypes which can surface into consciousness.
Our conscious viewpoint has a lot to do with psychic health and the amount of wholeness with which we live and experience life.
Certain techniques have been developed by our species over the last several thousand years to reach this center but it is full of pit falls and experienced help is often needed but not always.
http://www.thearchetypalconnection.com/SELF%20.htm