I never understood this. Ive seen many men, including friends that will cheat on their g/f or spouse with a female that is nowhere near as attractive. I dont cheat, but If I did...she would have to look AT LEAST as good as what I have or better. What is the point in cheating then? If you get dumped, you are left with the 5 instead of the 8 or 9 you had.
One of my serial cheating friends told me once about his cheating on his wife...... "if you have filet mignon all the time, sometimes you just want a hamburger" WTF????!!!!

Sound completely stupid to me.