When Can You Say You've Beaten a Multiplayer Game?

Growing up, beating a game was a big deal. Completing Super Mario Bros., Castlevania or Metal Gear was like a badge of honor and you wanted everyone to know. Games have changed since then but somewhere in the back of my head I still keep a small running tally of what is going on. Halo, Gears, Call of Duty, Killzone 2, Resistance, etc... all have something in common, they are great multiplayer shooters that have a single player component. You can easily say I beat (or finished) Halo 3 because there is a campaign that you can play through but what about games like Shadowrun, Team Fortress 2 or the recently released Battlefield 1943?

I am currently having a blast traversing the Pacific theater, taking over strategic points, killing people with my trusty SMG and crashing into trees whenever I try to fly a plane but the game got me thinking, how does one beat a game like Battlefield 1943? Can you claim superiority over the title once you max out your rank, reach prestige, achieve some other arbitrary factor or is it something else entirely? For that matter is it even possible to claim you've beaten a multiplayer game?

With no endgame the lines of understanding are not only blurred but completely invisible. Where and when can one actually claim they beat a multiplayer game or has gaming moved past such tangible badges of honor?

And can you ever really beat WoW? (outside of quitting the addiction that is)