it's bit vague question, and it seems you've already received much answers, but if you'd like more answers anyway, here's my 2 bits
General Tropes:
-> Extreme Fashion Sense, or Hairstyle/Haircolor of EVERYONE in the Game World.
Like i get that people might like to dress up, or dye their hair horribly (or sometimes natural? i mean wtf? how? natural violet hair? why? anime trope...) but there are people who just want to dress comfortably and not go with outright 80s fashion garb all the time.
-> Extremely Clashing Personalities, but poor Sparking.
It's a writing fallacy. When done right, it's really something, because it can develop the characters in the mind of the reader more than intended. But...this is the adult gaming market. the writing is Horrible. Just Horrible, about 70% of the time. People expect that clashing personalities would bring out some enjoyment in the debates, but it just gets agitating and gets on the nerves for the 13th time. There needs to be an outcome of "change" due to it, or it's just a pointless thing.
-> Character Motivation changes suddenly.
"For 15 years you have been chasing after you father's killer. but suddenly, you get captured, some guy tortures you, and after quite a bit of struggle, you suddenly start to enjoy his dick, get mind broken, and gives up on your 15 years of purpose, just to hang around the guy and get your daily dick juice while bickering with the others on his harem"
A+ writing. or not.
-> It's an All You Can Meet Women Buffet
Face it. Not everyone's a Rance. Too much chutzpah and no balls. there's no need to force relationships, but just an oversaturation of just girls in a story and no males to be found feels.... absurd. Especially when your the Male in the story. Not like, there needs to be a guy in the mixed shower in an all girls merrygang. It's just, there needs to be atleast an incline of a balance atleast
The Juicy Bits:
-> The Human Anatomy
As pointed in a above post, the shape of the body and size of the Important Bits in relation to overall physique. Aint nobody gonna have a G-Cup and not keel over as soon as they try to stand if they're not 80+ kilos heavy and a bit muscular at the shoulders atleast. If not about the art, but rather the scenes description, simple and straightforward words are the best.
-> Too much scene bulding
There are extreme bookworms who like... get off to "majestic thesaurus contents", but that's like not the general folk. getting too off the topic or getting too into details while describing the features and stuff ruins the immersion, cuz.... we have a dick in hand. the action begins when you say it, and suddenly changing lanes right before the climaxing traffic lights is just annoying.
-> Written *Sound Effect* Saturation
it's a common bad trope to have too many of those. it ruins the flow. nobody wants to read out "clap clap clap" "thwop thwop thwop" "thup thup thup" in the middle of the fire scene too much
-> Out in the open sex
if you do the deed where people can see you, just like irl, somebody's gonna approach you and talk about it. They dont just watch excitedly and move on or ignore the thing whatsoever like that.
-> "Every girl has the potential to be a thot/slut"
It's not. That just doesn't work. Corruption is a thing, but it can only go so far.
-> Sex goddess after the virgin run
You dont become skilled at anything by just doing it once.
-> Beastiality isn't harmful
._. fuck no, it's damn damaging to the body. i dunno why it's pushed off as a high orgasm inducing in some, and extremely torturous sex in others. The human anatomy is not fit to fit foreign things, and it's not something you can shove off within 5 mins, even if you "enjoyed it secretly". But that's just my personal trope gripe.
-> Women are weak willed creatures.
It's more like a mass fantasy at this rate. given that irl, bad things do happen on a constant rate, but they can be hella strong if needed, and not give up after 2 minutes of pinning down.
-> Ridiculous CG timings
It's more of a F95 thing. but much of the games here have a bad habit of the H-CGs being either too short, or too long. In the former's case, it's usually due to it being a part of the gameplay, possibly a game-ending event. And for the latter's case, due to overtly long dialogue that takes place during them. and if it's dialogue, by hellspawn!! the text box MUST be toggle-able. nobody wants to jerk off to a CG with a textbox saying some fucked up shit under it.
-> Cheap 3D Model Animation "Story" games
hot to some, not to others. there's no need to be 3D or full model animations. if story's the focal point, simple CG scenes are enough. If game, 2D models can work too, but too many people rely on the bad 3d modelers to spice up the games. it's just a big turnoff