For me it's:
1) High quality animations. Still images, slide shows, and slow moving frame-by-frame gifs suck. Animations should be fluid and natural looking. AVNs have changed a LOT over the past few years and tbh the old school type of AVNs that still try squeaking by without any animations in them just don't do it for me anymore. The first tag I hit on the search page these days is always animation so anything without them is instantly filtered out.
2) High quality renders. Not quite as important as the animations. Could be Real Porn, Honey Select/Koikatsu style models, hand drawn images, or even DAZ stuff. Just as long as the image quality and the characters look good. If it looks bad or it's text based with no images I'm not playing it.
3) Lots of animations/nudity. AVNs are fap fodder. If there's no fap material or it's stretched out between long periods of grind or story stuff I stop playing and uninstall. Would say (imo) that there should be at least 1 scene every 10 to 15 minutes of game play bare minimum. Would rather see one that has them every 5 to 10 minutes though.
4) Different Choices/Endings. Mostly play harem based sandbox games so for me the choices are what LIs to pursue and which ones to avoid because maybe that character is into a kink I don't like, or maybe this other one has a personality I can't stand. Either way having more choices and endings means maybe I can go full harem, pick and chose a smaller harem, or just focus in on one character for a more monogamy based relationship style ending. Can be fun, can be a chore. But it's better than kinetic novels since they're all on rails and lack any kind of player agency. So I'd say having lots of choices are required from my pov (since kinetic novels suck), but it's not quite as important as the animation and image quality.
5) Interesting Story. Okay, not gonna lie here; stories can be good, bad, amazing, awful, whatever. 99% of the time I don't care about your story. Not one damn bit. On a VERY rare occasion I'll pay attention to the story in an AVN if it looks interesting, but that's not at all what I'm playing them for and in *most* cases the more story a game has, the less likely I am to pay attention to it. I'm only playing Adult Visual Novels to see the Adult scenes. Full stop.
Anything else is just a roadblock or distraction. Could be a good distraction, could be a bad distraction, but it's not what I'm looking for at all.
So when a game starts adding in a ton of grind or dragging out the story on and on I'm either holding the skip button down until the fun starts or I'm just saying "Fuck this shit." and uninstalling it. When I want to fap, I'll play an AVN. When I want to read a good story I'll head over to B.Dalton's instead to pick up a real novel.
6) Long Life game. Preferred, but not required. Easily the least important aspect of the bunch for me. Game could be something you finish in 30 minutes, or it could be something that takes several days to complete. Just as long as it's got enough adult scenes and animations to justify the time sink. Personally prefer something that can be done in a single night or two, but there's a few exceptions to that.
These are just my personal opinions though so ymmv, ya know?
