When one prays to God, God hears it. When one prays to one of the "gods", the prayer is wasted. There are many places in the Bible, where it tells us to pray to God and also warns about worshipping "gods" as they are worthless and worshipping them relegates the person praying to worthlessness. I'm not sure how many religions worship the God of the Bible, but it would seem most of the major religions do.
If we agree that there is only one God, then there is no God of the bible, or the Torah, or the Quran, or any specific one, there is just God.
If a non-Christian prays to God, how does the one and only God, not hear that prayer?