Rape also involves lack of consent from one party, that distinguishes rape from sex.

How is adultery far worse than rape? If your wife cheats on you, well, it sure is no happy moment, but you divorce and look for another person in your life.

Maybe this is a cultural thing (I'm from South America), and you come from a place where it's ok to impose to your wife to have sex, as if she had no volition of her own and no authority onto her own body.