Think of it from this point of view. Arabs trace their ancestry back to Abraham through Ishmael. Christians and Jews trace theirs back through Isaac to Abraham.
Abraham had one god.
Good answer....except for the "Thou shall have no other God before me". That kinda implies there are other Gods. As well as the passages that mention "other God's and demi Gods".
So there is definitely more than one God. We're just choosing to worship Abrahams God, the Jewish God.