This may not be the most addictive game of all time, but in my mind, it is definitly the most flawless. Every aspect of the game, including the graphics, sound, and gameplay mechanics, simply could not reasonably be improved upon. The graphics are about as good as you're going to see on the N64 and the controls are as tight as could possibly be acheived.
My ONLY gripe is that locking onto enemies with the Z targeting can be a little difficult at times, but that's a small evil. Add the fact that this game will probably take you 50+ hours to complete the first time, and you have a game that is an instant classic.