Most people find cheating to be a rather icky thing to do. No matter how you feel about monogamy, it's pretty awful to lie to your partner and violate their trust by getting involved with someone behind their back. Of course, while most of us would hate to find ourselves in this romantic situation in real life, movies are a much different story.
Even the most loyal among us sometimes like to indulge in films about affairs. Maybe it's getting lost in a fantasy you know you would hate to fulfil in real life, or just the general excitement that comes from the movie's illicit love (or, often, straight-up sex). Whatever your reason for sitting through a film about a not-so-neat affair, there's more than enough movies to satisfy the urge. Hollywood adores some steamy adultery, so don't feel guilty about enjoying this genre.