Let's say you have multiple machines and have three friends over to play some pinball. How do you prefer to play?
--1-Player Games: Do you want everyone play their own game, so no one is ever waiting.
--2-Player Games: Do you want to play head-to-head so you have someone to play against, but you're not waiting around forever.
--4-Player Games: Do you want to everyone to play the same game with a four-player game.
EDIT: I suppose a 3-Player game would be an option if you there is one person there that no one else likes.