A PlayStation prototype of the game ‘The New Adventures Of Superman’ (commonly know as Superman 64) was just found: http://game-rave.com/?p=3123
Game-rave has a few playthrough videos on their channel, as well as a “review” video. Is it possible that the game is even worse than the N64 version?
UPDATE: Game-rave has just confirmed that the person who discovered the ISO will have plans to release it:
UPDATE#2: The game has been posted: https://archive.org/details/SupermanUSABeta1999-10-29