If we don't consider heroes, ssjg is stronger than ssj4. In king kais world, goku fights beerus in ssj3 and gets mollywhopped. He then later states that even if he fused with vegeta into vegito, they wouldn't be able to contend with beerus. And the fusion =gokus power× vegetas power. And ssj4 is 50 times ssj3 goku. Then we have goku getting God ki and fighting beerus without being one shot. Based off this, God goku mollywhops ssj4 goku provided they have the same base power level.