ai is enabling people to make smut games. ntr is popular. so the answer to your question is: a lot.
the funny thing is, that ntr "haters" go out of their way to search those games and give them even more popularity.
i see a lot more incest games and incest is a far more extreme fetish. ntr is vanilla. cheating is a standard porn plot. bored housewive doing the poolboy. a classic. but then again, doing your "step" mom and thereby cucking your father is also quite popular.