I know a bunch of nice guys. I give the ones who are unlucky in love the same advice: Never try to get a woman on the strength of your niceness.
It's not that women dislike nice guys, but bad boys are interesting. They have lives and qualities outside of politeness.
"But why doesn't she like me? I'm nice."
If I had a nickel for every time I heard that, it'd be a drag because cashing in my coin jar is a pain in the ass.
What does nice mean? Opening doors? Calling before the woman goes berserk at not hearing from a sleepover date? Paying for meals?
Those are all good, but they should be givens. Unless the quality of nice transcends ordinary humanity (I'm talking Jesus or Buddha niceness), it's not strong enough to mention. Aside from that, not many women I know would want to date JC or Buddha.
The idea of either of those guys on a date is starting to intrigue me.
I try to dissuade my male friends from throwing down the nice card. I tell them to go with real strengths. Even if the only thing going for them is the ability to touch their noses with their tongues, that would be better than the dreaded n-word.