Well here are my random ideas if I could make a game and do whatever I wanted:
-Open-world third-person action game (very similar to Insomiac Spider-Man games)
-No health bar for Metropolis, instead have jobber enemies that use Superman's weaknesses, vulnerabilities, and limitations of his powers against him to damage him: weaponize kryptonite, red solar radiation, nuclear attacks, magic, sensory overload, psionic attacks, high powered advanced alien/Apokoliptian weaponry, his solar energy reserves being drained, blocked off, or overwhelmed from overuse. His invulnerability functions like a 'shield' (or in Superman's case a 'bio-electric aura') and once that shield is overwhelmed after being worn down by enemy attacks, it would have to recharge. In that time his real health can be damaged.
-The first game has Superman start out very early in his career while he still learning how to use his powers and his body becoming more capable of absorbing solar energy as he matures which allows him to become powerful over time. This gives room for progression in gameplay.
-Certain attacks can ignore his invulnerability altogether (like magic) red solar attacks drain his energy reserves he needs to use his abilities, and getting hit by too many kryptonite-based attacks makes him sick, giving him a temporary status debuff which weakens all his attacks.
-No generic human grunts with normal guns for regular enemies, instead have Brainiac's drones, Phantom Zone Kryptonians, Lexcorp/Toyman robots, experimental monsters created by Cadmus, Intergang in bio-armor using weapons from Apokolips or Lexcorp soldiers in power armor using Kryptonite/red solar weaponry, parademons, Magic users/creatures, telepaths, criminal gangs using Lexcorp high-powered weapons other strong powerful aliens, other metahumans, etc. Interesting enemies who could pose a threat.
-Fully explorable Metropolis hub open world, with options to travel to the Warworld, Apokolips, New Genesis, The Phantom Zone, Brainiac's Ship, The Fortress of Solitude, Smallville, the Kent Farm, Lexcorp, and The Daily Planet.
-Main powers would be full flight, super strength, speed, heat vision, x-ray vision, and frost breath. Would upgrade these abilities over time as Superman's body grows more efficient at absorbing sunlight which is how he levels up. Later games would feature 'blue sun power-ups' which would give Superman access to abilities outside his normal ones and amplify his regular powers.
-Superman's ability to see across the electromagnetic spectrum would be akin to Batman's detective vision in the Arkham games which would allow for moments of investigation as both Clark Kent as a journalist and Superman (highlight enemies, see through barriers, people's body temperature, heart beat, track footprints, vapor trails, see fingerprints, etc)
-His abilities like invulnerability, heat vision, frost breath, or super strength/speed-based attacks should be tied to how much solar energy he has. If he overuses his abilities he would need to recharge them before using them again.
-Mr. Mxyzptlk reality-warping challenge/puzzle mini-game sections where he trolls the **** out of you.
-Warworld gladiator fights/wave combat
-Metropolis should have a unique look not look like any real city. Fantastically futuristic style, techno-utopian. It should resemble a place created by someone as intelligent, egotistical, and wealthy as Lex Luthor.
-Daily Planet, Kent Farm, LexCorp story sections where you play as regular Clark. This is where you'd mainly interact with his supporting cast.
-Have small moments of saving people, locating people in danger with x-ray vision, use super-hearing to locate specific crimes happening on the map, blowing away fire with freeze breath, lifting people buried under rubble, but also big set-piece moments of him catching planes, buildings, meteors (these would mainly take place in quick-time event/cinematics)
-Moments where you get to team up and fight with other heroes: Steel, Supergirl, Krypto, do combo moves with them
Main/side bosses: Lex Luthor, Metallo, Parasite, Livewire, Silver Banshee, Atomic Skull, Maxima, Zod, Brainiac, Doomsday, Mongul, Lobo, Darkseid