Hmm, the setting might play a role too in those player numbers. If there's one genre where sci-fi themes are being used way too much then it must be RTS. What is the last great historical/low fantasy RTS you've played? For many folks that is still Age of Empires II (for me I'd say it's Knights & Merchants, a much slower but more visually rewarding game), those HD re-releases surely must have made Microsoft some decent money by now? Although probably not enough to get Age of Empires 4 underway.