Fantasy, Sci-fi and Supernatural are the favorites, it seems. It makes sense, after all, games set in Aravorn, Planet Stronghold(using the anime style, unfortunately) and Nicole are good examples. I really think that "Supernatural", "Sci-fi" and "Fantasy is far reaching, like, could go from a vampire game to a horror one; or have date sim's in Aravorn, not just RPG's(like Heir's and Grace) or different kinds of Sci-fi(Planet Stronghold and Bionic Heart), so it's quite possible to have some differences in the same genre.
To me, what really matters is the story. I prefer those settings for having stories full of potential, like, anything could happen in them. A setting in the modern world is a bit "boring";- it doesn't mean the game isn't good, just that I won't be impressed by it since I already know what to expect, like the game Roommates were in a simple slice of life setting, and even so, I had fun; but games like Nicole had me on my toes and really got my attention, even if they took place in modern times.
The characters are very important and sort of give color to the setting that you're playing, like, Loren got a lot of praise for not making your character the "chosen one" hero for saving the world, but more like a side-kick for the main character, that is, Loren herself, but even so, it was about the journey, the growing as a team and as a powerful working force to save more than the typical "the world", but the very society that oppressed you. So, characters like Loren and a fantasy setting like Aravorn really makes a difference in whether the game will be appreciated by the fans of good writing and good games in general, although, it's a shame that the majority of the date sim's/visual novel players are so attached to the anime style kind of art. Planet Stronghold was one of the best games I ever played from Winter Wolves and one of my favorites from all time, even if didn't received the love it deserved, and one of the reasons for not selling as much was the card battle game play and the more realist art style, like the American comics style used in super heroes stories.
So, it's safe to assume that stories a good anime style(please, choose an anime artist that doesn't make the characters look the same or strange) like Queen of Thieves or Loren, with a good story and characters that keeps the player interested in it would be the best way to go and the genre used for the setting(based on this pool) would be fantasy, sci-fi or supernatural.
I would suggest that like this pool were made to choose the favorite genre, there was a pool to choose the artist for it(like, putting some examples of each one available to make the game art and only commission after getting the results) and the kind of romanceable character each option(GxG,BxB,GxB,BxG) would like to have in the game. Like, a bad boy or a goody-two shoes for BxB, a shy or temptress for BxG and so on.