A few things:
1. For the most part, men do not cheat because of low self-esteem, "entitlement" (whatever that means, exactly), ego, or "mental illness" (lol). These are explanations women make up because they don't understand men. Men cheat, or want to cheat, because the vast majority of them find sexual variety pleasing in and of itself. You know how you'd probably end up bored with your favorite food if you had to eat it three meals a day, every day? This is exactly the same idea. Yes, I am aware that this impulse also exists in women, but it doesn't seem to be *nearly* as strong.
2. Many men who cheat are nonetheless good fathers, brothers, sons, friends, employees, even good husbands in every other way. If male infidelity were driven by some kind of underlying personality disorder, that wouldn't be the case.
3. Men do differ. A few find it easy to be faithful. Some find it damn near impossible, even with the best of intentions.
4. Surveys consistently indicate that there are a lot of people (of both sexes) who refrain from having affairs only because they worry about the potential consequences. I guess reasonable people can disagree about this, but I don't see any difference, morally, between actually cheating and staying faithful only because you're worried about getting caught.