Ever since playing the Batman: Arkham series, I've wanted more superhero games done in that style, albeit with changes to the combat system.
Particularly, I want a game about The Question, aka Vic Sage, aka Charles Victor Szazs. Although it likely won't happen due to his mostly unknown status (though his appearance on Justice League Unlimited back in the day helped with this), I think it has a lot of potential.
Some of the problems I have with the Freeflow combat system from the Arkham series are that Batman can fly around the entire room to attack thugs. This reduces the realism of Batman (considering he isn't supposed to be the superhuman), and makes Batarangs less useful. I would alter this system so that there's a much bigger limit on attacking enemies the further they get from your current location, thus making gadgets more useful and adding a little more realism.
However, The Question doesn't really have any gadgets, so to speak - his only real one is his belt buckle, which releases gas that makes his mask adhere to his face and his suit (and hair) change color. Therefore, I'd make improvised weapons a more useful part of gameplay. In Arkham Knight, Batman can pick up blunt objects like baseball bats or pipes, and smack enemies down with them. They were useful as they ignored the defenses thugs could acquire (such as stun batons and riot shields), but they broke after a few attacks. They would no longer break, and Hub City would be far more littered with them, making such weapons more available for both Vic and thugs. He'd also gain the option to just throw anything he picks up, to fill the niche of attacking enemies moving to a longer range.
One of the key aspects (if I remember correctly) of The Question is that the mask isn't what defines Vic - it merely frees him to do things that he wouldn't in his civilian identity. Because of this, I'd add the option to allow Vic to swap into his civilian identity, assuming there is no one else in the area. This would do two things - firstly, the corrupt Hub City police and regular thugs wouldn't attack Vic on sight - they'd either ignore him or attempt to mug him. Secondly, it'd change Vic's fighting style to a more undisciplined, less martial-artsy style. Think of a person that doesn't really partake in hand-to-hand combat, but can fight regardless.
Finally (at least from what I can think of now), Vic Sage doesn't have the resources Batman does. Therefore, he's not going to have detective vision (which I found stupid anyways). He will pick up and find clues the old fashioned way - think of a system similar to L.A. Noire's clue-investigation sequences, except perhaps without audio cues. The removal of detection vision additionally ensures that should there be any stealth sections in the game, Vic Sage doesn't get free wallhacks.
The Question is a neat character. However, thanks to his status as a C-List hero (or possibly even below that), the possibility of this game happening is extremely low unless he gains a sudden surge in popularity. Oh, and I have no idea what the story would be - whether it'd follow his Dennis O'Neil run, or something more original, I don't know. Regardless, I'd be happy to see the game made at all, unless it completely destroys Vic's character.
Man, I sure hope he shows up in Injustice 2 and isn't garbage.