I think there is a way. Superman is no human. He is a god among us.
So let's him discover new worlds for us.
Give him a camera and start broadcasting documentaries for the BBC on other planets.
Imagine a Superman game where you could travel between planets yourself, getting asteroids out of the way. Confronting other inhabitants from his original planet, fighting hostile demons and monsters in super planets, and odd worlds. Worlds where Superman could be as interesting as a human, where his super powers would be really necessary rather than making him inmortal. :smile2:
I'd love to program a game like that myself.
From time to time he would be back to earth to visit his romantic interest.