We have tried to make a comprehensive list of game genres (and sub-genre) to help you present your game idea. We understand that in some cases, the game idea you have may not fit into one of the genres that is listed; in these cases, we recommend you pick the genre that is closest to the game you are presenting. From there, you can further describe the game and the genre in the Short Summary section at the end of the Game Submission process.
A good example of this would be if you want to create a mystery game. There is no selection for mystery under any category because it could actually fit into many categories. A Mystery game could potentially be a Puzzle, Narrative, Roleplaying, or Strategy Game. Or... it could be some of all of those. Pick the one that feel the most 'right' and describe what you really mean in one of the other fields of your submission.