I have some theories of my own, but I'd love to hear what everyone else thinks.
Most Helpful Guy
Women are looking for strength of character, self-confidence and a sense of mystery - traits that are often lacking in a "Nice Guy". An inner strength wrapped in a quiet, confident man is an attractive trait for many women. "Mr. Nice Guy" may come across as needy. He may share his emotions and experiences that belie his insecurities. While he is telling his women friends about the problems in his life he is being labeled as a loser in the love department.
"Nice Guy" has a hard time making a decision and rarely takes command of a conversation. And just like the rest of us, he just wants to be loved and will do just about anything to gain your acceptance.
"Nice Guy" is the guy that looks to please a woman without pleasing himself. Doing whatever it takes to make his woman happy.
Women love a bit of mystery and that is what a "Bad Boy" gives them. "Bad Boy's" are able to keep that sense of attraction we all feel in the beginning of a relationship, where it is new and exciting. "Bad Boy's" do this by taking risks and staying independent.
When women date a "Bad Boy" it also does lots for their ego (not his). They feel a sense of empowerment to contain the "unattainable".