Well it's not really the "bad boy" attitude they're attracted with. I think that can be confusing and misleading. "Bad Boy" attitude - a criminal behavior? reckless? jerk? I don't think any women wants to be with a jerk.
I would say - they like confident, assertive men with goals and discipline such as taking care of their hygiene, clothes, and body (not to the metrosexual level). The "too-nice" guy is viewed as weak and unable to take charge of anything. They like to have a man in charge. That can PROBABLY be viewed as a "bad boy" but it's really a man in charge which means you gotta be an asshole sometimes.
the "too-nice" guy are lacking in a few important, desirable departments such as body, appearance, and the mentality. They may be childish/immatured... not too social when meeting with her friends (yes woman likes to be impressed by her man in front of her friends)... not wanting to change themselves to better themselves... and.. sadly - not to sound superficial but... nobody wants to be seen with weak/unkempt guys. and who wants to see their guy being walked over by somebody else? It's depressing.
Meg - if your friend's being upset for a couple weeks... then tell him to stfu and be a man. lose that emotional baggage FAST cuz nobody wants it. 
Emotional baggage only gets him a good female friend, not a gf.
