I'm not sure where to begin on this topic, so I'm just going to start.
I think there are 3 main factors to any game like this that determine whether or not its enjoyable.
1) Why its done.
Take for example your basic cheating/NTR situation. Stable if boring married couple and some other man out to enjoy the wife. Now it can be looked at as "This guy is here to enjoy himself with the wife at the expense of their marriage and will eventually step back and watch said marriage implode, taking a FWB out of it maybe."
It can also be looked at as "This guy has found a good looking woman in a soul-crushing, boring marriage and wants to have some fun while giving her an outlet to explore and experience things she never would have had she not strayed.
The first has either disinterest in or malicious intentions for the target of their desires.
The second, while not moral, actually has something in mind that is more than just taking and abusing.
Witch Trainer has an MC that is somewhat amoral and detached from the world. He has no interest in Hermione beyond getting to do naughty things with her and scrambles her mind, reputation and eggs in the process.
There was another trainer out there, forget the name, where the MC takes in an abused ex-slave. He works on her, like training, to open up both emotionally and sexually and not be afraid of intimacy. Granted, she wasn't innocent, but I think it is a decent example of "corrupting" someone for their benefit.
I would think that the more predatory the story it is, the more it would engender those guilty feelings.
2) How its done.
I think one of the things that this genre depends on is that aspect of corruption that entails getting the target to do something outside of their comfort zone and eventually enjoying it.
The heroine could have lost a bet to the MC, and is obligated to have sex with him repeatedly. While her doing so in a perfunctory manner allows the MC to have fun, that is not where the thrill comes in. The thrill is that moment where, when he is kissing her during it, she gets excited enough to kiss back.
That moment when the target is either forced or drawn out beyond what they would usually do and willingly does it and enjoys it is the moment of interest.
Aesthetically, having the process done realistically and slowly "boiling the frog" is preferable to some unrealistic hack of a hypno-app or having such a wonderful penis that she goes full slut after the first interaction, but that isn't the core of the issue really.
Looked at from the perspective of the author, any innocent girl, married woman, or anyone with intimacy issues all have the same problem: How do you start them on this path?
The one extreme is the tactic of forcing them repeatedly until they get used to and and resign themselves to their fate, which in and of itself is somewhat unrealistic (see Illusion games for example).
The other extreme would be where the MC leverages an existing relationship and emotional bond to talk his partner into slowly getting more and more experimental and extreme.
In between is a whole spectrum of bets, lying, cajoling, imaginary aphrodisiacs, hypnosis (techniques and applications) and blackmail.
I would think the more the storyline is to the forcible side of the spectrum, the more it would raise those guilty feeling.
3) To what degree its taken.
What is left behind after the action is done? What is the end result for the heroine?
Cute, innocent girl with a super-slut secret identity?
Openly sexually predatory person?
Wife addicted to cheating, but had adapted to concealing it well?
Ex-wife addicted to cheating who has developed a sadistic streak and posts videos of her adventures to her broken ex?
Sex-addled nymphomaniac whose mind broke ages ago and is now posting adds for transvestite Great Danes to have adventures with?
The more stable and sane a character that is left behind, the less debased the heroine is, the better she has been served by the experience, the less the guilty feelings.
There is almost always some form of wickedness involved in these types of stores and games, but it has a broad spectrum and people will feel "off" at different points, according to their tastes.
Its like lying. There are degrees.
There are white lies: "Your skirt is fine. No one can see you're not wearing panties."
Lies: "Its just a kiss."
and damn lies: "I've had a vasectomy."