One thing puzzles me. The more "unconventional" fetishes a game has, the more the storyline is repetitive for games with the same thing.
Well, there's constraints due to the fetish, but mostly it's due to a lack of imagination of the author and/or it's lack of knowledge regarding the fetish. Many authors add this or that because it seem to be expected by the players, but have absolutely no idea of what it mean.
Take watersport by example. It's often added because it's easy to make it optional, don't need hard works... at least as depicted in games since 95% of the time it's just a scene where you'll look at the girl pissing while in the toilets. One authors added this in his game. Few others found that it was an easy way to add a fetish in their game, and they copied what he did. Then some authors find it in many games, always made in the same way, and thought that it's something that mandatory for a good game ; but having no idea about what it effectively is, they also copied what the others did.
But my main question is, plot is pretext for erotica or vice versa?
Both ?
Ideally, you should write your story (at least the general idea of it), then when it's a coherent story that can works by itself, you add the lewd parts to it. But there's people who do the opposite and still achieve to have something interesting. And, obviously, there's those who don't care at all about the plot, and they still can find their public.
The deeper you go, the more other people like it despite the weaker plot (I mean predictable and banal).
This is only due to the lack of alternative. The deeper is your fetish, the less games you'll find, therefore you'll play whatever game have it.
But the same also apply the other way. There's games I play because I really like the story, while not liking its lewd content. It's by example the case of
Shatered. I don't like sissy games and male on male content, and it's a sissy game where male on
malesissy represent a third of the content. Yet I really like the deepness of its story, play all the updates, and follow 9 routes of the story. There's also few games where I find the lewd content boring, but for which I'm hooked by the story.
So what is the point here?
What if there isn't ?
Look at movies, there's some ridiculous ones that are among the best popular success. It's the case by example of
The Rocky Horror Picture Show. It's a (relatively badly done) movie released in 1975 that is still played in some theaters around the world ; do you realize, near to 50 years that this movie is played at least once every weeks, is there another movie that can say the same ? It even ended in the Congress Library due to its cultural importance.
The same happen with books, like
Twilight that is a horror in terms of writing, a stupid story and an insult to a whole literature's mythology. Yet it found its public and was a great popular success. Or there's
50 shades of Gray, that isn't better in terms of writing qualities, and depict domestic abuse, not BDSM, but also was a success.
And those are only three examples, there's many others, including in video gaming, music, and probably other fields. Too which you've to add the "average" books, movies, video games and music, that achieve to exist because there's a public for them. It's a small public, but in the same time a public big enough for them to be more or less to be cost effective, and justify that their author continue to works.
Just write the story you want, the way you want, and take pleasure doing it. If there's a point here, I'm pretty sure that it's this one.