I agree with you partially
NTR is related with jealousy but it is focused and the player... or the reader of the story
When I read a novel or a game I do not like to play with a loser protagonist...
I want just put an example:
If James Bond (007) were a loser, the movies would never have been successful ... and all bond-girls stories starting with NTR!
So in my signature you can find only winner MCs (male or fameles)
The MC must be a winner.
to write someting about a loser MC it is required the skill of a great drama writer.
Okay, where should I start...
I was just describing the common structure of ntr (someone who loses, someone who wins, and someone who get 'stolen'). This is the simple structure which is base for most ntr-stories.
At this story, you can play as the loser (which is mostly implied, because of jealousy) or the stealer (which will let you enjoy the jealousy of other people, if you ask me). You also can make a perspective of the 'stolen' one, but for me this would be more cheating in a game, than ntr (just my opinion).
You only like winner MC's, okay, this means you just like netori (and definitive NOT netorare), but others want to read about a guy who loses someone (which doesn't mean he has to be a loser)...because: jealousy.
What defines a MC as loser, the fact he got his partner stolen?
Or if he is portrayed as wimpy, small dicked and unfit?
What if he is a big manager, makes lot of money, is good in bed, has decent penis, but his wife cheats on him?
But that is another point: storywriting. The most used one is the second one, and the bad guy is the third one, and sure who wants to be the ugly guy, when he can be the other one, so I understand your position.
For me personally: I surely can play games in which I lose someone, but as I said in previous post: a game is meant to be interactive, so to take away my choices (or just don't let them count) is a something I (!) don't like.
Which brings us to shitty stories...almost every game/manga with ntr follows the same lame plot: rape/blackmail leads to sex, which leads to "Oh I stay with bad guy, because he makes me feel sooooo good" and this is bullshit...
In the real world this only could work where woman have no rights...so not in japan/europe/usa (mostly).
Why do we still like it? Because we want to fap, and when you have to read 30 pages of manga to see nude a nude girl, you won't read it, so at page 10 you will get your fapping reasons...
Written stories (choya, literotica etc) can use some more time to build-up, because when you are willing to read a text you will be ready to wait. And surpise, surprise: written stories will often have a more plausible plot...
And with games as far as I could say: I want to see that my choices will have an impact on the story, but also: most people want to fap, so first rule if you want to make money with games: show something which often means story is mostly...flat.
So what do we learn from all this: fap = no quality, but quality = can't be short (at least for me).