They're two characters from entirely different universes, with different roles and different power balances. They're heroes who simply wouldn't fight each other. We don't allow these kind of discussions because it is moot.
If there's a crossover and the author wants Goku to win, Goku will win. If the author wants Superman to win, Superman will win. Until that time, there's no answer to this and nobody is more right than the other.
There is no debate. Both you and your friend are wrong.
