The way rooms are meant to be categorized is based on the how the game is played rather than the gametypes themselves. When considering which room to put your server in, don't think of what gametype you play, but rather if the game is played as a platformer, shooter, fighter or anything else.
Standard is meant for "how the game is meant to be played", i.e. as a platformer. Here, the focus should be on platforming, and should be played more or less like singleplayer is played, regardless if it's 2D or 3D. It's important to note here that this does not mean that it has to be cooperative; both race and competition should go in here, since they still focus on platforming!
Action is meant for games that are played more like a shooter or fighter, like Ringslinger or Battlemod. These are often competitive, but doesn't have to be! Ideally, if there is any focus on violence, no matter how soft, it should be in this category.
Other is self-explanatory: if it doesn't fit the description of the other rooms, it goes in here. The typical gametype that goes here is Hangout, but other gametypes that don't fit other categories like SRB2Ware also goes here.
These are just guidelines are not hard rules, and doesn't have to be followed, but are general good advice if you ever plan to do some serious hosting.