God is an omnipotent, omnipresent, omniscient, omnibenevolent being featured in many Religions and spiritual groups as the loving, sole creator of all. (A god, as opposed to the God, is a similar creature, but as appose to being a sole, loving being, a god is a member of a group with varied select powers over nature or people in various mythologies).
He/She is mentioned and referenced in the Riddick movies. In Pitch Black there was a discussion between Riddick and Imam Abu al-Walid about how Riddick chose to say: "I absolutely believe in God. And I absolutely hate the fucker!" in response to Imam's belief in God. Later on, when the group were in court in the rain and Riddick stated "Where the hell's your God now?!" This came full circle when Riddick chose to rescue the others, and Imam stated "There is my God, Mr. Riddick!"
God does not personally physically appear in the movies, but is believed by many characters to be the influence of the good things, as well as the destiny of Riddick, but not necessarily by Riddick himself.