On this topic, I like to play female-protagonist games as an anal-slut without them having a relationship. When there is a male-protagonist, I like to have the girl only for them in a relationship. I don't know if you guys agree with this.
(I hate NTR, however, I am not against such games getting added to the list.)
yup, I also like that if the protagonist is female. In that sente games like Project Myriam are fine imho.
When the MC is male, I like to have a favourite girl and focus on her --although games like My Pig Princess with its great art makes it difficult for you to have a favourite-. Like say the big sister of the MC in Insexual Awakening....
I also love the family setting of people living under the same roof where the MC can have several girls, some of them -or all of them- related to him, and do naughty things and a setting that leads to very erotic situations.
Aside from Insexual Awakening, The Twist for instance is an excellent game in that regard. Also Business of Loving and Hot Sand of Antarctica (though not all the girls live in the same house), Summertime Saga.....
Also good trainer games like Witch Trainer Silver Mod where you can train several girls can be amazing.
As for the rest of what you commented, I usually prefer girls that love anal sex over anything else, and also virgins or nuns that love it when they try it, and similar.
The issue with many games is that it's hard to build the tension and the desire to continue playing after your first encounter. After than, when you have anal sex with the, the scenes either repeat or the progression in that sense stops.
So I usually stop playing some games that I really liked because there seems to be little else left to do.
Other games are excellent games that you love to play and you are enjoying them so much and there is a girl that you like and then after a lot of time you find out that you start with a scene where you can't choose with hole of her you want to penetrate, and you're somewhat forced to an scene you can't choose.
Ideally we'd have games where the MC can have anal sex and over time it can evolve to many erotic situations and not just have anal sex and then you see no progression in that regard. I mean, more anal scenes.
It's tough to create a game that is both so engaging and varied without being too grindy at the same time. In some games you have a feeling that you grind a lot just to see that anal scene you're eagerly waiting for but the game kinda stops after that.
Games like Brothel King, with users add-ons, rarely get boring 'cos of the varied scenes, but you have many girls at your disposal, and you're always looking for the next anal queen, which is very engaging and fun. But for some reason some girls can have vaginal sex after a while depending on some traits evolution, dunno why, but it makes pure anal sex girls more valuable, though the same can happen to some of those.
As for fun and engagement... Window Girl, is a very engaging game with simple mechanics but you need your time to master it, and it's so fun to get the girl in the mood to have anal sex with her.