I would've said George burns but he usually add a comic style to it for example "OH GOD YOU DEVIL" which he acted as God In 1984, Morgan Freeman and Morisette aren't bad but they don't just cut it for me. The reason why I will prefer George burns it's because despite the fact that a comic role im playing God will definitely not bring the best even still he manages to add a bit of flare and style which keeps you wondering how long it took him to master the role however the three actors you mentioned are not really the best for the truth is that George manages to do so well in a comic setting playing God.
Morgan freeman does not have the accent although he has the authority and the seriousness as well as the command but there is something about his accent that gave his action away have not seen so many movies which played god except one I loved his performance but if you must know playing god requires a unique accent which morgan freeman didn't cut it out for me.
Alains Morisette has the accent not totally though but his performance was not commanding and it seemed as if the character was imposed on him that is he didnt blend well with the character and he felt kind of lost.
So George does it for me especially with that his classical 1984 movie which I think you definitely need to see
Morgan Freeman. Morgan Freeman's voice is such that he can say anything and it will sound like the greatest thing since sliced bread. Morgan Freeman is unsurpassed at playing God. It is said that men should not play God but, IMO, that does not apply to Morgan Freeman.
But then I'm a big fan so I might be bias
However, I think he adds a person touch when playing God. Like that role is natural to him