In pretty much every video game crafted in existence, at some point, you're competing against A.I., or the CPU. While in some games, like Madden or NBA 2K's Franchise modes, or the campaign of any FPS or fighter game, this is all well and good, but eventually, you crave a need to test your skills (Read: absolutely destroy) against human competition. There are several games out there that allow you to do this. In some cases, over the development of a game, fans have sent the game developers feedback as to the chances of including a MP mode in a game that otherwise doesn't have one. Such as 2K's foray into FPS multiplayer with BioShock 2.
In my personal experience, I happened to enjoy this game's multiplayer - it wasn't as ambitious as say, Call of Duty, Halo, or Killzone, and it knew it wasn't, but it offered a satisfying experience, especially considering you can use a wide variety of Plasmids and weapons on other players, rather than A.I. Splicers, Big Daddies, and Big Sisters over and over again.
An additional benefit of a multiplayer mode is that it can drastically extend the amount of time someone plays a game - people STILL play older Call of Duty games to this day. And since I personally enjoyed the BioShock 2 MP for what it was, I feel that several other games can benefit from this experience as well.
I'm a technologically savvy Sony Gamer born in the epic city of New Orleans, currently pursuing a degree in Mass Communications in South Carolina. When not losing hours of my life with a controller in my hand, I'm probably losing hours of my life typing endless words into a keyboard, my attempt at this thing called "technology journalism". Hi there.