God King is one of the starting choices for your Economy Policy slot. The usefulness of this policy is dependent on your Capital's starting tiles, and the general geographic situation of the particular game. If there's ample Production potential in the terrain, God King can be used to get extra Gold and a pantheon quickly. However, if an early source of Faith and/or Gold is found -- such as a local religious city-state, certain luxury resources, or fortuitous Tribal Village discoveries -- it may be better to rely on Urban Planning for the Production boost. In either case, God King will rapidly lose its luster once trade networks are established and Holy Sites are built and should generally be slotted out once a pantheon is discovered.
Not satisfied with being mere kings, some ruling dynasties took on the mantle of divinity to insure obedience, prestige, and infallibility. Egyptian pharaohs were generally believed to be incarnations of the god Horus. In imperial China at times the emperor was considered the “Son of Heaven,” ruling under the “Mandate of Heaven” with his commands believed sacred writ. Some Roman emperors were declared gods by the Senate, but generally after their death, so godhood didn’t interfere with their duties. Although all this godliness was eventually replaced with the divine right of kings to rule, it has echoed throughout the course of civilization.