There appears to be a resurgence of focus on 2+ player games: Gears of War heavily relies on it, Nintendo built a console around it, online play thrives off it, and the world's largest games publisher is betting on it (EA's Army of Two). While 2+ player games are nothing new, they arguably aren't praised or reviewed as well as single player games traditionally have been.
On the topic of the best multiplayer games, one Slashdotter opines: "From my own experience and research, it looks as though a top 50 would include games such as Streetfighter 2, World of Warcraft, Speedball 2, Super Mario Kart, SWIV, Ikaruga, Stunt Car Racer, Super Monkey Ball, Puzzle Fighter, and Mario Party. Whether they are competitive or cooperative, Slippery slope or Perpetual comeback, 2-player or multiplayer, retro or cutting edge, I want to hear [what your favorite multiplayer games are]!"
We do too. What are your favorite 2+ player games?