Who created God, if God created everything?

If you go back hundreds, and perhaps even thousands of years the great sages of the major religions have agreed on one thing. If the religion they represented believed in one Supreme Being, God, they all described God as not fathomable by human beings. God is beyond our understanding, and therefore God may be outside of time and space. Makes sense if God created the universe, since scientists say that even time and space did not exist prior to the big bang. In that case -- if God created the universe he is not subject to time. Nothing came before God. God is eternal and has always existed.