Alan Noble writes,
"Cooperative gaming has been around for a long time, from Gauntlet in the arcade to Double Dragon on the NES. The draw of this style of gameplay is that you can play with a friend (as opposed to taking turns) in a non-competitive way. If you have a friend over who has never played Halo multiplayer, you can always play split screen co-op through the campaign and both have a good time. In addition to "story" or "campaign" co-op, modern multiplayer games usually include a "team" mode which encourages cooperation, modes like "Capture the Flag" or team "deathmatch" or "slayer." In these modes teams benefit from working together against the opposing team. In practice, this often results in a competition to see who can get the most kills on a single team. Your "opponents" might technically be the opposing team, but actually every player in the game becomes (to some extent at least) a challenger to your score (whether that be flag captures or kills). In my experience gaming, I have had only few matches where I honestly felt like I was working together with a group of players to achieve something as a team instead of seeking a high score against other players. For Christmas, my (lovely) wife got me Left 4 Dead, and since that time my conception of cooperative game play, and gaming in general, have changed."