I must say that sadly a game about Superman is not a great idea, for similar reasons to why Zak Snyder's films suck so much. The current, modern Superman is not very interesting. An Alien Jesus who's some candle for mankind, saviour of the universe who moves planets when he coughs doesn't make for an interesting game or movie.
IMO, the *best* part of Superman's mythos is a) dual identity, journalist by day and secretly a superhero and b) cool powers of flight, strength, breath and heat/laser vision. His completely invulnerability to everything but kryptonite is shit and the main issue with trying to make a game with him. If he is always invulnerable and capable of beating any threat, there's little real challenge. Thus one of a few things would need to happen.
- He faces threats that are a challenge
- His immune-to-everything ability gets ignored for the sake of an enjoyable game
- The threat must be against something other than him.
IMO, the first is boring. Battles of the Titans are boring outside of Greek Mythology. Eragon book 4 is testament to how utterly uninteresting it is to watch/read about invulnerable Gods duking it out. The MOST interesting Superman moments are Clark Kent having to hide his identity, having to find a place out of sight to change into his costume, saving a falling plane or pulling a man out of a car. These things we can relate to, they're super heroic and memorable.
The thing is DC hold him up as the very God he's portrayed as by Snyder and held up as. Everything post-Reeves makes him out as a Messiah, a deliverer, instead of a hero who saves Metropolis and the like. I think take away his complete invulnerability so he can face mundane threats (or hand-wave it off as everything is kryptonite/magic) will make it so we face a challenge, have a story based around Clark Kent/Daily Planet/Lois Lane/Lex Luthor and forget the light-for-mankind bullshit. Make it a sandbox in Metropolis/faux NYC, let us level up his strength/heat ray/flight speed and Bob's your uncle.
His Godhood/invulnerability is his worst trait and why modern Superman sucks.