Really though, I have found loads of NTR games, but why isn't there a lot of NTRing games (I guess they are called Netori). I don't want to be NTRed, I want to NTR. If you know a good Netori (NTRing, as in you are the one NTRing smb else) game please tell me. If its a RPG, and it has a male protagonist its better. If not, its okay as well; beggars can't be choosers ^^
Does the male who you are cucking have to stay around? Because if not I suggest you look at any of the incest harem games where dad is still around. I didn't get far enough in My Summer with Mom and Sis to know if dad sticks around or not, but he's in the picture at the beginning and mom is a relationship option. Milfy City is too early to tell, but mom is very displeased with dad sexually and has the hots for you, so that's a thing.
Other games that I can think of:
Incest Adventure - dad is an asshole who's cheating on mom, and you start fucking mom and end up getting dad arrested and out of your life forever.
The Artifact - dad is
and as a result isn't giving mom the attention she deserves, with the artifact's powers you sleep with her twice in the guise of your father before continuing that relationship as yourself, after she's found out. Dad isn't out of the picture until the end of the game so this is actually a good example, unless you need him to watch as well.
View Of Family - this one I add tentatively... while not revealing the plot too much, your dad leaves your mother at the start of the game. However if you play the game right you've fucked his new woman already by the time you're getting sexual with mom. However, you don't know that yet. That said, you later find out and between you and your mother devise a plan that involves taking advantage of that further to get back at dad and the woman. That said, idk if the game is on hold or what but I finished it in early january and don't think its been updated yet, so this plan hasn't happened yet.
Big Brother - See, most people are worried about how Eric is gonna NTR them, but don't realize that the goal is to cuck eric.
I Love Daddy - I know you said male MC, but I like including this one because the MC begins fucking her dad in front of her mom as the game goes on.
The problem with all of these examples, aside from The Artifact, is that none of them really focus on the fact that the woman is cheating with you. So you don't get much of a chance to really revel in it beyond your imagination. Maybe, as Milfy City continues you'll find some opportunities for that. Also, while I don't know it you will in MlWM&S you can always try it out.
I didn't get far, but iirc Timestamps has you sexually interested in the married woman who is the "landlady" so she's a possible route for that too, but I haven't played enough to know for sure.