Definately one of the greatest games of all time, if not THE greatest.
Gameplay: What more could you ask? This game set the standards for action/adventure games and is very much perfect. Link has a wide variety of moves and techniques as do his foes which makes the game both challenging and entertaining. Hyrule is a large kingdom and there are so many things to do if you so happen to get bored/stuck on the main quest.
Graphics: Excellent, some of the best looking on N64. It really puts you into the game and makes it quite realistic.
Sound: Another perfected aspect of the game was its sound. I personally enjoyed tune at some point and I soon found myself humming along to the song. There's little voice acting in the game, but a Zelda game never needs it in fact it may even be better off without it.
Value: You can't not get this game, it is a lengthy quest with plenty of side quests which occupied me for close to 100 hours (and thats not including the Master Quest version of this game which took maybe a further 30 hours). It has great replay value, you'll just find yourself revisiting this game over the years wondering why you ever stopped!
Final Words: Get it in some form or the other if you haven't already, or your going to regret it BIG TIME!