[Which means you can download it][link]. This Superman is a prototype which was [eventually renamed Sunman][sunman], with the logo changed. [Sunman was never released, but it is fully playable][sunplay]. It is not at all the same [Superman game released by KEMCO for the NES][nes]. Gameplay is very similar to another Sunsoft superhero game [Batman: Return of the Joker][bats].
[link]: http://forums.lostlevels.org/viewtopic.php?t=2015 “Lost Levels :: View topic – 24 new dumps, including 2 unreleased games”
[nes]: http://en.wikipedia.org/wiki/Superman_(Atari_game)#Superman_.28Nintendo_Entertainment_System.29 “Superman for the NES”
[sunman]: http://en.wikipedia.org/wiki/Sunman_(video_game) “Sunman”
[sunplay]: http://www.lostlevels.org/200311/200311-sunman.shtml “Sunman on LostLevels”
[bats]: http://en.wikipedia.org/wiki/Dynamite_Batman “Batman: Return of the Joker”