I have been thinking about this issue for a while now.
The whole nice-guy/jerk split is a false dichotomy. It's an attempt by people who aren't satisfied with their lot in life (mainly "nice guys") to dodge responsibility. By painting themselves as the white knights ("nice guys"), they effectively convince themselves into thinking that it's not their problem they don't get anywhere, but the rest of the world's problem.
The problems "nice guys" have is that they are:
1) Too needy; they seek validation WAY too often.
2) Afraid to straightforwardly ask for or pursue what they really want; they defer to others' judgement and preferences WAY too often.
3) Not interesting; they rarely take risks, even calculated ones.
4) Not confident;
I realize nice-guy syndrome affects whole ranges of life, from relationships to friends to employment, but let's take women for now, because that's what others in this thread have discussed.
Consider 3 guys. #1 is the epitome of a nice guy. #2 is the epitome of a jerk. #3 is...well...let's call him the "bad boy".
The guy and his girl are walking down the sidewalk. They're dressed nicely, and she's wearing fancy open-toed heels. They come upon a puddle.
#1, the nice guy, offers to carry her across the puddle.
#2, the jerk, jumps the puddle and berates her for being too f***ing slow.
#3, the bad boy, jumps the puddle, lightly teases her while smiling a bit, then comes back and carries her across.
See? #1 was so eager to help that he came across as a lap dog. #2 is just a, well, jerk. #3 exploited "push-pull" - he pushed her away with some slight teasing, then pulled her back by doing the right thing. He exploited tension.
Let's take another - the guy's girl comes crying with some huge story about how her best friend did such and such. You know the kind of huge dramas that women come up with.
#1 listens for hours and hours, attempting to fix the problem. He becomes her emotional dumping ground; her psychoanalyst.
#2 says "shut up, tell someone who cares" and goes back to watching TV.
#3 listens for a bit, shows some sympathy and says "I know you feel rotten right now, what a horrible thing for her to do.", holds her a bit, then distracts her with another activity, or by sleeping with her.
Again, #1 is trying too hard - she doesn't want someone to fix the problem, she wants someone to understand. #2 is a jerk. #3 understands what she really wants - a sympathic ear, and then to be distracted by something else.
Guys there is no nice-guy syndrome, it's a failure to determine what women really want. You can be the most moral, polite, upstanding, upright guy in the world and still be a "bad-boy" by simply knowing when to tease, when to be sympathetic, and by never, ever, ever supplicating.
Nice guys and jerks BOTH finish last...it's just that jerks can pose as "bad boys" better than nice guys can.