I would play something like this.
A game where you're the people are bent on holding you accountable for the destruction you cause.
The only thing that makes Superman interesting is when his humanity is questioned or when his faced with moral dilemmas. You have to choose between being a 'boy scout' or 'whatever it takes'. Both have their pros and cons. Maybe a system where if you're too 'good' it's exploited as a weakness. If you go the 'whatever it takes' route you lose the support of humanity and maybe they even reject/hunt you.
Hell, to keep it simple you make it open. Create a story where Superman slowly loses his humanity as people demanded more from him/he grows jaded. Or you start off as a Superman who must regain the trust of the people because he caused some catastrophic event or something.