The 4 player adapter is to the PSX as the Light Gun is to the N64. Not a lot of Games that let you use a Light gun on the N64

I think you ment the NES not the N64, I could be wrong, but I don't know of one game on the N64 that uses a light gun, I don't even think there is one. And the NES did at one poind ship with the gun, the PSX does not ship with a multitap. Correct me if I'm wrong here.