When I first started playing online games, I would tell people "gg" if I enjoyed myself during the course of the event. It was rare that I ever play a game where victory or defeat hinges more than loosely on what I accomplish in a battle. When I played tribes for example, my forte was that of screening with a scout. I would scour the middle of the battlefield and reduce the numbers coming into our base, chase down flag runners and whatnot, but at the end of the day the ultimate keys to victory lay in the meticulous individuals who would turn the flag rooms and generators into nearly impenetrable fortresses and that foolhardy lot that prefered to spend their time in brutal close quarters combat.
It seems odd, but back in those days when text was the only form of communication available I was more attached to my team and their actions. The same goes for the enemy team. It seems strange but in Tribes, if both flags were taken a common occurance was the epic flag duel, where opposing flag carriers would fight a 1v1 battle for possession of the flag. I can't even begin to imagine that level of sportsmanship in a modern FPS game.
These days, since I tend to play games on a console I rarely even bother donning my headset to communicate with other players. As often as not, my own team (and my opponents) do not represent a communal effort at having fun, but rather a group of individuals who seem to delight in being the biggest bastard possible. Sometimes, most notably in Battlefield: Bad Company, I will congratulate my squad on a job well done because when a squad is willing to work together, a player can experience a great deal of joy. L4D is notable as well because the adversarial mode, when well matched makes me thankful for the work my own team has done as well as that of the opposing team for offering such a significant challenge to our progresss.
I think this trend probably originates in sporting events, where win or lose a team is forced to shake the other team's hand. When I played baseball it always seemed like a triumphant march, when we lost it seemed like I was signigng the documents of submission. In short, it never seemed genuine back then.
As a fencer, one is required to not only shake the opponents hand, they must also salute them at the beginning and end of a bout. From time to time a match is so one sided that nothing is gained by either myself or my opponent and I always resent having to shake a hand then. Most of the time however when I fence with all the skill I can muster and my opponent does as well it matters not to me if the score is 15 - 3 because even in these bouts both of us can be commended for delivering the best effort one can. Before I ever played an individual sport I never realized just how important it was to be able to say at the end - that was the best I could have done.