You guys have to be kidding are you all out of your mind, the best multiplayer FPS has to be Aliens Versus Predators 2 Gold Edition, so versatile and hard. Was the most intense FPS I have ever played.
For single player of course you have to give props to Doom, Wolfenstien, Rock, Quake, Golden Eye, Half Life, and Dukenukem, but I have to say the best one, the only one would have to be the original Punisher for the regular Nintendo, it was kinda an adventure game I guess you could say cause you didnt control your movements, but it was a point and kill. On That note Judgement day and the Waynes World Aerosmith games were some of the best as well