Ocarina of Time was a special game. It was one of the original N64 titles that transitioned 2D into 3D. I maintain that OoT is the best 3D Zelda game thus far, and for me I doubt I will ever play a Zelda game that tops the overall OoT experience.
I could sit here and tell you why OoT is so special to me:
-riding Epona for the first time
-running across Hyrule field and watching the sunset
-spending hours fishing
-pulling the Master Sword out of the stone
-time travel between adult and childhood
-8+ temples (3 kiddie levels, forest, fire, water, spirit, shadow, AND ice, bottom of the well, Ganon's castle)
-the hookshot in 3D
-side quests that felt meaningful
-challenging and original puzzles that have simply been re-used way too many times in the newer Zelda games
-Gerudo fortress
-killing chickens/riding chickens
And as Xantar noted, the game was perfectly paced and I personally think OoT has a modestly sized world.
The answers in this thread are in my opinion very obvious. Everyone knows OoT is the best 3D Zelda game.
What I don't get is why this thread is not about Majora's Mask. I feel like Majora's Mask really gets shafted. I personally think Majora's Mask is strangely underrated and perhaps just as good if not better than WW and TP. And Majora's Mask is the only 3D Zelda title to actually make strides towards originality post-OoT. What's up with that!
OoT > Wind Waker > Twilight Princess aka Original > Sequel > Sequel
OoT ---> Majora's Mask aka Original --> Evolution with Innovation