I voted Ocarina of Time, but I think I have to go with Majora's Mask, to be honest.
Majora's Mask may have been a bit shorter than Ocarina of Time in terms of the main story and dungeons, but what it lacked there it made up for in side missions, minigames, and character depth. I absolutely love the soundtrack too and really need to get around to learning more of the music on piano - since my book has been shipped and is coming in any day now, I'll have a lot of fun with that - and many times find myself just standing in an area to hear the music (the Clock Tower especially). I just love everything about the game. Getting the masks is still an incredibly fun thing and the effects many of them have are really cool. I also love the gilded sword, such a cool weapon.
Basically, yea, everything is amazing in that game. Zelda at its all-time best, in my opinion.
God, I need to play that game again, it's been far too long.