''What if God was one of us?'' Jim Carrey cockily warbles in ''Bruce Almighty'' (coming out Nov. 25; PG-13, 102 mins., Universal), a movie about a modern-day doubter who receives divine powers, only to abuse them -- levitating ladies' skirts, toilet training his dog, etc. But Bruce is just playing God. The real God is Morgan Freeman, who first appears as a mop-wielding janitor, a far cry from those booming-voiced, white-robed Supreme Beings of old Hollywood. Yet Freeman's life-size God isn't exactly a new idea. George Burns was essentially delivering the same I-help-those-who-help-themselves message in ''Oh, God!'' (1977), as a deity who listed among his mistakes tobacco, ostriches, and avocados (''I made the pit too big''). Both, in their deceptively whimsical ways, are Creators who, yes, become one of us, but who do so in order to impart their infinite wisdom in terms we mere mortals can understand -- an idea that's been around since the New Testament.