Well, if we go to statistics, you might as well suggest for every dev to make a visual novel with chapters and very little playability since those are the "games" that dominate the lists by popularity. Sadly those are exactly the media I'm not looking for, so if everybody was doing only those, being at this site would become pointless for me and many others, so yet there exists a niche for devs like akabur and his Witch Trainer.
So, my suggestion would be to any dev to make a game they want to make, what they would like to play and what their skills and resources allow them to do, see if catches wind and if not, then do something else. There are already enough burger-games, burger-movies, burger-superhero-shit and every kind of other entertainment made based on statistics and they are all more or less crap and most of them fail. Not because they don't interest the people as a concept, but because there can be only so many things in one niche that compete for peoples certain itch and when that itch is filled, they move to something else for a change, which is usually some niche the statistics aren't supporting.
In the gaming industry the statistics won't matter shit, as the whole industry has been built on niche that by statistics at one point was thought doomed to fail and the same trend has gone on and on. FPS was niche at one point, so was RPGs, strategy as well... Actually all but arcade was niche in the beginning and not supported by statistics and thus considered doomed to fail by the money men.
So with all undue respect, I can very well tell you up where you can shove your statistics.
PS. As far as porn games go, they are still considered a niche overall in the industry, as what kind of perverts would play them - right?