I'll have to go with Nintendo 64 for sure. Ocarina of Time was my favorite Zelda game, and Majora's Mask also hits high on the list. The games on the other systems were very good, but I believe that the Nintendo 64 games were better.
Ocarina of Time was an absolutely amazing game... and I just can't get over it. I know, I know. Ocarina of Time fanboy. For some reason I just really loved the game. A lot of it was due to the fact that it was my first, but I also believe there are a lot of other factors that contribute to it. The game was just very enjoyable, no matter what I did in it or however many times that I played it. I always have fun playing that game, and I just love it more than all of the others.
Majora's Mask was also a very good game. Like I said, it is one the highest ranked on my list. Alongside Ocarina of Time, it's one of the greatest Zelda games ever. We've had many polls on here on the favorite Zelda game, Majora's Mask vs. Ocarina of Time, and whatever else. Majora's Mask and Ocarina of Time just seem to be the better of the Zelda games. The three days idea was fantastic, and made the "moon falling into Termina" theme pop out at you even more. It also added a new level of challenge with that time limit. The masks were wonderful, sidequests fantastic, story appealing, and dungeons very enjoyable. Overall, it was a very good game.
These two games are preferred by many over the other Zelda games, and make me show my opinion that the Nintendo 64 generation of Zelda was most certainly the better of the classics.