I get weary of male acquaintances complaining about being single and blaming it on them being "nice guys because girls don't like nice guys". 99% of the cases where I hear that complaint it is from a person I wouldn't class as a nice guy. A fun friend, perhaps, but sure as hell not someone I'd date or anything. You are single because you THINK you are nice and do nothing to better your ways.
Just a little rant.