I find the naming convention for anything related to NTR to be incredibly confusing but for me it mostly comes down to the fact that when playing as a male main character I tend to just unconsciously imagine myself as the main character, as opposed to a female character where I don't do that. As far as what I do and don't like:
If the protagonist is male:
- strongly dislike seeing "my" girl(s) cheat on me with another guy
- strongly enjoy seeing "my" girl(s) cheat on me with another girl whether MC gets to join in or not (if MC gets at least some token action as well that adds to it for me)
- strongly enjoy MC having the chance to convince/blackmail/whatever my rival's girl(s) to cheat on them with me, especially if they know it's happening or better yet are watching
I agree, however, some games give you the opportunity to "win back the girl," which is more baffling than the NTR itself, why in gods name would
anyone want to put effort into trying to win over a slut who left you due to for sexual gratification?
That being said, it could be a decent jumping-off point to tell other stories. For example, a guy finds his a video of his wife getting railed while she talks about how he sucks in bed and his dick is small etc. So, the husband decides he is going to get revenge and launches an investigation to find out more. During the investigation, he finds out the guy she was cheating on him with has an attractive fiance(the heroine) who is unaware that she is about to marry a cheater. Once he tells her, they decide to team up to take them down.
With this premise, the story can go in so many directions that an interesting story writes itself.
- A romance story of the MC and the guy's fiance as they both struggle with trust issues as they fall in love with each other but they both aren't sure due to the infidelity of their previous partner.
- A hardcore BDSM story in which both partners are captured and subjected to the kind of shit only seen in hentai.
- A simple revenge story in which both girl and guy manage to succeed but don't hook up, however both of their cheating partners are left homeless, penniless, and shunned by their friends and family.
Though it would be a massive undertaking, you could also roll aspects of those into one game and add in other endings such as:
- The guy divorces his wife but fails to get his revenge or win over the heroine, but at least manages to move on with life.
- The guy fails to get revenge but manages to hook up with the heroine, even though they don't get revenge they take solace in the fact that they at least found happiness in each other.
- The NTR good ending, guy manages to win back his wife.
- The NTR bad ending, the man decides that his wife's happiness is what matters most and he should just live with his wife's cheating lifestyle because he wants to stay with her no matter what. So, he starts to support both the wife and her boyfriend financially while they have sex in front of him as he watches in tears but does nothing to interfere.
- Lastly, really bad ending where the guy, failing to acheive anything he set out to do and left with no hope, he kills himself. To rub salt on the wound, when the wife finds out rather than feeling bad she celebrates. As, since she was married to him, all of his assets are hers, and now that he is out of the picture, she and her new boyfriend can now have a more open "legitimate" relationship as they live it up on everything her husband worked for.