I was contemplating jokes about why a stock market game could be considered "fantasy" or even "comedy" (or perhaps "mystery"), but that wouldn't be helpful for you. :)
I've had a similar problem to this with writing, where a story might not fit so neatly into a genre, or it straddles multiple ones. Rather than suggest a category for you (since it's really arbitrary and ultimately up to you), I'll offer a strategy:
Rather than look at your game and see which categories it fits (which could be many), I'd look at the categories and see where you'd like your game to be, both in terms of any connotations you might have about the category and what kind of audience might choose that category.
In other words, choose the category that allows your desired audience to find it most easily. If you were looking for your game (or a game like yours), where would you look for it first?
Just my take.