I think it's a bit more mixed than that. I only like ntr if it's cheating, and not sharing, for example. So if the MC wants his gf/wife to cheat, or actively tries to get her to sleep with other men, I just alt+f4.
If the wife is just straight up cheating, but the mc knows about it, but actually likes it. Then it's kind of in the grey zone for me. I still get off from the betrayal part, but it's dampened by the mc liking it.
A good example would be Italian slutwife. The mc is a pathetic cuck, so I don't like him, and don't get off to it... BUT. If you go for the NTR route, his wife is still out there slutting it up behind his back. So her betrayal balances out his willingness to a certain degree.