Most multiplayer games have a relatively short arc of play, often centred around a single match or event. The match is decided in favour of one player or the other after the event, which is less than an hour long.
What would it look like to play a game that had a much longer arc? A week, or a month? It would have to look a lot different to the kind of game that takes an hour—nobody could take the kind of stress that StarCraft entails for a week straight. In order to fit around other things that people do in their lives, like work and sleep, it would have to be in some measure asynchronous, not demanding attention on its own schedule but shifting to match that of its players.
There exist games like this, but not many. EVE Online is 24x7 and continuous, though recently added the ability for corporations to choose their primary time zone, protecting their bases while the players are asleep. Neptune’s Pride and Subterfuge are match-based, with matches lasting a week or more. There are other multiplayer games which are played for a long time which I don’t think fall into this category: World of Warcraft, for example, while it has a persistent multiplayer world, it doesn’t have an arc of conflict that reaches beyond a single play session.
If you consider games as play-acting or fantasy, all these games enable the fantasy of being a military commander. As fantasies go, it’s a pretty attractive one—for the player, because power and control feel good, and for the designer, because a military context provides a clear goal (defeat the other side), a clear source of conflict around which to build the core of the game, and a rich set of metaphors and history to draw on. But it’s overdone, don’t you think? Surely the space of interesting conflicts extends far beyond the military kind, perhaps even into things that are relevant to people’s daily life. The sadly defunct Leap Day is an interesting example: it was player against system rather than against other players, and winning generally required a sizable measure of cooperation.
The inimitable Dan Cook has written at length about games as life-long hobbies. Could a single match be a life-long hobby?