The Legend of Zelda: Ocarina of Time is considered by many to be the "greatest video game of all time", and in my opinion, it has earned this honor. When this game came out, people were apprehensive about how Zelda's transition to 3D would go. But Miyamoto and his team blew everyone away with this fantastic game, which is complex, intelligently constructed, and beautiful.
More than that, however, this game defined a generation of gaming. For some people, the transition to 3D was proving to be the "awkward teenage years" of gaming. But with OoT, all fears were dispelled, and 3D became the new standard.
Never before had a game world been so immersive, or so real. The locales were realistic and beautifully rendered, and the characters were all unique, and had a certain charm about them. The sprawling adventure-story worked fantastically to highlight the more subtle aspects of certain characters. Everything in this game was so well put together that even now, 8 years after its release, no other game has yet dethroned it as "the greatest game of all time."
Maybe I'm just too much of a Zelda fan, but I think it is safe to say that, beyond any doubt, The Legend of Zelda:Ocarina of Time is and will remain the greatest video game ever created.