They should just make a game where Brainiac plants gigantic kryptonite towers into the earth that irradiate the planet. So Superman loses all of his abilities besides his OG powers of being a strong guy who can jump high, and as he destroys these towers one by one, he gains some of his power back (leveling up). Of course the towers are protected by Brainiac-bots and mind controlled villains and each tower has its own design plus its size determines whether Superman can reach it without taking damage, so you have to start with the small towers and work your way up. In between you can do side quests of stopping calamities and bad guys taking advantage of the chaos, which builds up a ''trust" level with the citizens, based on the amount of people who still believe in Superman. This level could give additional boosts like faster healing, quicker recovery of special abilities and additional help/routes in the towers.