First and foremost you need a good story that can stand on its own, it shouldn't HAVE to be movie based game or tied in to the movies, and second you need a committed and willing group of developers that will take their time and do the game right.
It needs to be open city.
Fully destructable and intelligent environments.
You need good, smooth flight and running mechanics.
The fighting needs to be smooth simple yet engaging
Take advantage of full use of all of Supermans abilities
Great voice cast, and story like TAS (the game has to be about Superman, don't overcrowd it with unnecessary hero and characters)
Unique missions and challenges.
Easy upgrade system.
Visually pleasing graphics and animations.
Tell me, how would you make a good Superman game?