I don't think you will find anyone who loves to be cheated on. Nor will find many people who want to be lied to, deceived, or betrayed. No one wants to be made a fool.
As for the other woman or other man, yes they are in the wrong for knowingly being involved with a married or attached person. However the person committing the actual betrayal bears the brunt of the responsibility.
A cheater essentially is looking to address his or her needs/wants on "the side" while holding onto all that is "good" in their primary relationship. It takes "courage" to end a relationship long before you start considering seeing another person. Therefore cheating is a "cowardly" act.
Some people treat relationships like jobs. They won't leave one unless they have another one lined up. Having said that I believe there are three basic cheaters.
1. The Incessant Cheater - This person has never been monogamous. Most likely enjoys flirting and using sexual innuendo whenever the opportunity presents itself. Very often he or she is also attractive, charming, magnetic, or fun to be around. Their motto is "variety is the spice of life."
2. The Unbelievable Opportunity Cheater - This is someone who would not normally cheat however "the stars lined up perfectly" for them to get with someone who is "out of the league", someone they've had a crush on, or even an ex from many years ago. Very often this person will come clean months or years later to purge themselves of the (guilt) they carry around each time they look into their loving mate's eyes.
3. The Discontented Cheater - This person feels "justified" to cheat. They feel their partner neglects, abuses, or takes them for granted. However they may not necessarily go looking to cheat but it wouldn't take much for an "attentive stranger" to put a smile on their face and in their heart. If caught they will either blame their mate or claim it wasn't "planned". "One thing led to another." In other words their mates brought this upon themselves.