I know that not all supernatural beings are considered to be gods but where do you draw the line? In some religions (esp. animistic ones) ghosts are believed to be the spirits of the ancestors and they are worshipped like gods in other religions. So for these people what a Christian or Muslim may regard as a ghost, is a god.
And as we all know, the gods of one religion are often seen as evil demons by an other religion ;)
So in my opinion there is no supernatural entity that cannot qualify as a god since the only criterion it has to fulfill is to be regarded as such by someone.
My own working definition of a "god" is any being which is not subject to the laws of nature. That certainly applies to the God. It would also be true of less powerful -- and perhaps non-existent -- beings, such as devils, demons, nymphs, Zeus, angels, etc. Gods don't die (but I don't know what became of the Titans), they don't get hungry (although the Olympians put away a lot of ambrosia), they fly around, they perform miracles, cast spells, grant wishes, etc.