There's a reason it's a classic
Obviously it's easy to say that a game is the greatest of all time and indeed, the term is bandied around more often than would be thought possible; but in the case of OoT it is fully justified as an epic adventure takes you through over 10 enormous, complex dungeons which require more than mindless key searching. Evidence of this is found in the fact that the words 'Water Temple" still cause thousands of gamers nightmares.
But while you're not scrabbling in one of Oot's extraordinary dungeons, you can undertake any one of dozens of side quests, all of which are unique and allow you to explore, which is a reward in itself in this game. Exploration is one of the key components of this game, one which makes the world feel alive and far larger than any which came before it. In fact, many third gen consoles fail to create the sheer feeling of scale that comes across in Oot.
There's a reason Gamespot gave it ten, and there's a reason i gave it ten. Play it and you'll find out what it is.