The two powers, God and Satan, would not be equal in Divine Ranks. God will be much higher.
God's priorities will be Faith, Tradition and Love. Satan will promote a self-focused pride. In the west, this will manifest among the people in a warmongering, conquering attitude. In the middle of the lands, this will manifest in an over-inflated sense of human arrogance in their own accomplishments. Satan will be more subtle and indirect. The current attitude across the world will be in Satan's favor, while worshipers of God have more isolated pockets.
In the far east, in the more greek-styled cultures, the rebellious Outsiders have attempted to establish their own faith system. While not possessing divine ranks or the ability to grant divine spells to Clerics, they'll have accumulated their own power with class levels.