I think the "nice guy" thing is a bit... There are two types, really. Some are genuinely nice guys who get overlooked because the girls like guys who are being mean or macho instead of the quiet, polite type (in which case, these girls can be fools). Others, expect that if they "play their cards right", they will earn the right to have a relationship/sex with the girl. The main difference is that the latter usually expresses this in such way: "Oh come on, I took her to dinner for 3 times and I didn't even get a lousy blowjob?!" They might also be the type who go for the really, really pretty and vacuous girls whilst being average looking themselves. They fail to realise that those girls are interested in money and looks and mr. average doesn't have enough of either, and they also put down girls who might be average-looking and interested in them "Urgh, she's too fat/has a big arse/small tits/whatever"
I kinda know, as I was a girl version of the former. Nice girl, but not girly enough. Nice girl, but seen as a friend. It wasn't until I found my genuinely nice guy (who I've been with for 6 years come friday), I realised there might not have been attraction. You can't make mutual attraction happen. If you happen to be a nice guy, who the foolish girls ignore, you will have to wait until they're women who will appreciate genuinely nice guys.