Showing God with a big G, is the way we show respect to those that are of faith and believe in the God of the creation that is also supernatural and personal to the believer; a God with many human-like characteristics.  This includes all the thousands of Gods that man has ever created that are supernatural. The Supernatural Gods of traditional religion are not subject of the same laws of science that govern the rest of the creation including us sentient beings.

In comparison, a small g god is simply the creative force or forces that were and are the cause of the creation; the transformation of energy into matter during the creation of the universe and everything in it. The small g god is not a personal god and is not supernatural and is subject to the same laws of nature and of the universe that the rest of the creation is subject to.  

A small g god is not supernatural, is not anthropomorphic (with human like traits and characteristics) and therefore is not jealous, caring, loving, or kind, does not need to be worshiped and does not listen to thoughts or prayers, is gender neutral, is fully reconcilable with the laws of nature, is simply the energy behind the force or forces from which everything in the universe originated.

The concepts of big G God and small g god are further set forth in The Distinctions document.