Ocarina of time without a doubt. In my eyes, it is still the best game ever made. Nothing has come remotely close since. Even now, 7 years on, i can still pick up that game, and totally immerce myself in the world for a couple of weeks worth of play. Nothing gets frustraiting, its all pure enjoyment on every level. I'm usually very tough on my ratings of games, but aside from slightly easy bosses, there is nothing i can really critasize the game on.
As for older RPGs, Landstalker for the Mega drive tops it. A brilliant game through and through, though it is obcenely hard at times and very frustrating towards the end. But as it is, it succedes in the Ocarina way by making the story supreme.
Notable mentions go to Links awakening, A Link to the past, Shenmue, and Wonderboy.
(Note i am not a fan, especially in the post 16 bit era, of turn based games, i believe it is obsilite, madeningly slow, and just generally far more boring than a real time RPG. I was put off FF7 after the 10th random monster battle. :evil: )