I personally think the only way to make it as simple as it should be is to not have the sub options at all. Cause once it starts, its going to be a flood gate of stuff basically making every game its own seperate sub-genre.
RPG
Sports
Shooter
Action
Adventure
Fighting
Platformer
Do we really need much more than this?
The more I think about it...the more that I'm starting to think that *ANY* sub-genres will quickly end up being more trouble (and , naturally, creating lots of arguments/debates about "what goes/doesn't go where...and why")...which will, in turn, take time, focus, & effort away from other things that are more worthy & important of the...time, effort, and focus/attention.
IDK the best "Answer/Solution" -but- I'm thinking maybe a site-wide consensus/discussion/vote on making sure that any & all
MAIN
genres are represented & accounted for (or, easy enough to add later, if originally over-looked)...may well be the best, least troublesome, and simplest & most stream-lined way to go.
You all owe me another 2 cents...again!
I agree with Soera and Disgaeniac.
There are really only two solutions: 1. Stick with broad and simple genres (no sub-genres needed) or 2. List every imaginable sub-genre. I think the best way to be thorough and cover all bases is to have a complete list of basic genres. That way it's less of a headache for everyone involved.
EDIT: Also, Foxhack is right: puzzle, strategy and rhythm (or music) should be included. Along with simulation and racing (and possibly survival horror and education?). That would round out an all-inclusive list of genres, I think.