You skipped the SNES, which was long lived and a very popular system only had one Zelda games, also the original Gameboy only had one (if you consider the GB and the GB Color to be two separate systems as I do). I must also say that the quality of the franchise is less when the quantity is more. Majora's Mask felt like a rushed work in order to cash in on the excitement of OoT.
EDIT: Oops, I didn't see the with the exception of the SNES part when I first read your post.