The best game, in my opinion, for generating a sense of actually being Superman (or any other superhero) is Freedom Force. This game's range of heroic activities, from up-rooting trees for use as clubs to leaping from building to building in pursuit of villians, is unsurpassed, even by City of Heroes (does City of Heroes allow you to hurl cars into the sides of tall buildings, causing a satisifying crumbling of half of the structure?). The main campaign takes place in the 1960s and features original heroes whose appearances, along with the backdrops, are unquestionably based on Jack Kirby's work. Though this part of the game is great fun, where it really shines is in its system for creating or re-creating your own, or popular, heroes and then unleashing them against each other. Unfortunately, a lot of websites offering skins from Marvel or DC have been shut-down due to threats from said companies. This site,
www.alexff.com, still gives access to a huge collection of skins in addition to offering "recipes" for re-creating your favorites heroes! Even if you can't find the skins you want, it's a great deal of fun creating your own.