Without being rude, how much have you actually put yourself out there? I've seen a few friends do it and their social skills always improved at least noticeably. Perhaps you're labelling yourself as "below average socially" and this is hurting your self-confidence? Obviously, if you go into a room feeling unconfident it's probably going to affect the way you interact with other people/body language etc. And when you say you've spent years working on it, maybe you're overanalysing? That would probably make it harder for you to socialise
Also, are you hanging around with the same or similiar groups of people? I used to have a lot of very "academic/intellectual" friends through doing a particular hobby, who knew me from a time I was slightly more introverted. I didn't entirely "click with" and relate to them at the start and I didn't till I moved away and we no longer hung out, either. Some types of people just don't "gel"; I get on perfectly with other extroverted people who are into partying and sports and all that, and I'm fine with that.
So maybe try interacting with a new group of people? if someone already sees you as "the awkward person" it can be very hard to change that perception. Also, without stereotyping people certain groups (especially the geekier types) can be very hard to break into plus having relatively bad social skills themselves - sometimes it isn't always your fault.
Nobody "has" to read stuff like "The Game" or "The Rules." As said above, stuff like that will almost certainly get you more of a reputation for being a bit of a weirdo (no offence) than anything else, what with the outlandish stuff they proclaim. But, as to why some people are good with the opposite sex without ever picking up a book like this, again it comes down to social skills. Knowing how to get on with people. Nobody's just "born" that way.