Ocarina of time is not only the best game in the Zelda series to date, it is the best game that has ever been released.
Why? Everything you could ever want to play in a game- that's why. It's a fairy tale. Boy grows up different from his friends, and is one day called to see his race's mentor, and told he is destined to be a hero of his land. 60 hours or so later, he is the Hero of Time- savior of his land.
The graphics are still pretty good by 2004's standards, but the sound is just, well, incredible.The land of Hyrule is full of great music, but the ambience makes you feel like you're actually there.
Basically, there is very little wrong with OOT, but the Water Temple will go down in history as the hardest level EVER. Other than that- perfect.