Ok here is how you make a superman game.
First you make the game about superman with unlocking his powers by leveling him up like you do with spiderman. But instead of getting stronger Superman learns more control from his powers.
So in the begining the player is will have supes powers but it will easily go out of control.
Life meter is a solar meter, when low on health you go to where the sun is shining most, if there is a cloudy sky then his regen is slowed. Kryptonite would be in the game and you as superman have to destroy them, with the help of batman telling you where to find them. Wonder woman and bats and flash will show up and you as a player chose the moral standard.
But in my game there will be 2 paths to choose that superman has no say, his character will not be changed by player moral compass, but where the player wants the story to go.
So if they want a bad darker setting superman will be corrupted by dark sied, or superman does what he does best.
You unlock stuff like
Super strength- this is obvious he can lift things with out problem but crushing it is another.
Steel body- where attacks like bullets and heavy punches dont take away that much solar energy
Het vision and x ray vision
The more you upgrade the easier it is to control.
Super speed and flight- both allow you to go faster but in bullet time you will have more control of your inertia
Ice breath - more control
Villians- lex, brainiac, and dark sied.
Some villians you have to show self control others you will be allowed to go all out.
Story- i would make 3 story lines 2 would be expansion packs or the 2nd story line would have a different world setting. Like first one is metropolis, 2nd wpuld be a city of magic, 3rd would be an alien planet or earth and apocalypse.
First game will deal with Luther and Doomsday as major antagonists, then brianiac and leech and the magic dude, theb last one will be dark sied and freeing people of apocolypse or conquering it.