How is the idea that our whole universe is merely a simulation inside someone else's computer practically much different than the idea of there being a "god"?

How is the idea that our whole universe is merely a simulation inside someone else's computer practically much different than the idea of there being a "god"? From a certain perspective, they're one and the same. They can both change the universe arbitrarily either by changing the rules of the simulation or the state of the simulation. I agree that both are incredibly unlikely, but you can't say for certain that it is not so.