2. Super Smash Bros. Melee (4)
No other multiplayer game has consumed as much of my time as Melee has. This game seems to somehow get better with time. While it lacks some of the features of its sequel, it simply has a better feel to the gameplay that made it far more addictive. The characters were unbalanced at times but never so much that it really mattered except at the highest levels of play. There were a number of features tailored to groups larger than the number of controllers available that allowed you to rotate people into the game without figuring out whose turn it is to sit out. One of my favorite arts of Melee was that you almost never felt like the characters weren't doing what you had wanted them to.
Primarily an RPG player but have interest in any game that will make me think.