We already have lots of tags for specific games, but if we generate the levels of traffic we'd like to generate, then we're likely to find that for the most popular games people will want/need game-specific tags.
Where there is a lot of traffic relating to a particular game, it would make sense to have multiple tags for that game that would enable users of the site to separate and manage the traffic.
I suggest that we adopt the convention that a tag that is specific to a game should have the name of the game or an abbreviation of the name, then a . and then the tag, so for instance we might have asl.movement for movement in the Advanced Squad Leader games. Game tags should continue to be the full name of the game, so advanced-squad-leader.
I'm not sure that "movement" is necessarily a good tag, it's just the first example that came to mind!
This came out of a discussion in the comments to this answer, for context.