It depends on my mood, really. Most of the ones I end up liking have the MC win at least sometimes, or in some timeline, at least. MC's who are complete losers tend to ruin it for me.
I really don't understand why this is such a big thing for people. They are pixels. They don't really have feelings. As far as my personal tastes, it depends. Cheating is a kink for me. This doesn't mean that I want to cheat or to be cheated on, but it is something that I like to explore in some of the games that I play.
I feel NTR can be okay. I usually feel a strong disconnect from the character it's happening to, so I can enjoy watching it happen to someone else, but wouldn't want to happening to my self insert if that makes sense.
I don't mind it if the MC is the one doing the cheating and mostly its like if the bf is a dick or something and if its incest mom cheating with son. Those are really the only ways I like it
I think it's funny, specially how some people have such visceral reactions to it, like if theres even a possibility that a harem game might have NTR they throw a tantrum, and it's ironic cuz in harem games the ladies are often getting NTR'd by the protag.