It is saying that means that men that are overly nice won't have a good success in the dating, or business, or sports world.

Hi Shen! This is an idiom. The phrase is referring to the idea that people who cheat, or are ruthless, end up being more successful, while people who follow the rules and are gentle will be left behind. It's not meant to be factual, but a humorous way to look at the idea that people who are "nice" don't get ahead in life. (I'm a nice guy, so I disagree!) Ryan