Psychology
As a therapist, I often see the following happening: person A says something, than person B, who has known person A since a long time, says: 'no, that's not what you're real motivation, you're real motivation is...' After this, person A tries to convince person B (s)he is honest about his or her motivations, but person B doesn't believe person A because (s)he 'knows him/her so well'. Well guess what? In most cases, person B is WRONG and (s)he should just listen to what his or her friend is saying.
A similar thing is happening here: MythusMage, there seems to be a general consensus that the word 'hobby' has some negative connotations, just as the word 'game' has. This said, I submit to you that no one word will invoke the same associations in everyone. The truth is, there are NO UNIVERSAL associations. There IS a larger percentage of chance that a given word will invoke specific associations on a whole, but there's NEVER a 100% chance that EVERYONE will associate with the same things.
This said, it DOES seem most people here don't find the word 'hobby' 'clicks' with them better than the word 'game' does. Chances are, it won't 'click' better with the general populace, either. I know this is hard to accept as it apparently infringes on YOUR world view, but the fact is that world views differ and apparently the prevalent one regarding this concept is: it won't work. To be sure, one needs to do marketing research and even then there will be a large margin of error.
I would also like to note many of the name changes you propose have already been used. (For example, in the case of the DM, 'Keeper of Secrets' in Call of Cthulhu, 'Storyteller' in White Wolf Games, etc.) Also, the emphasis you want to lay on RPG's is one many gamers already use. Most mature players like to 'ROLE-play, not ROLL-play', and most of the points you've raised are automatically implied when you try to act out a character 'in-character'.
Many many many RPG's include great roleplaying tips, which form the basis of what you call 'a guidebook'. 'Amber', for example, dit this very well. I also don't think ROLE-playing and rules are mutually exclusive: I personally like interesting, realistic rules, or interesting gaming systems, such as the ones found in The Dying Earth RPG, Hero System, Silhouette, Rolemaster and more. But my no means does any set of rules exclude acting out what is happening. In fact, I'm a published writer myself and I review lots of stuff in our own Dutch-language sf/fantasy/horror magazine at
www.fantastiek.com.
Although I don't like hack 'n' slash, there's a market for it and you'll lose many potential buyers if you decree THIS GAME SHOULD ONLY BE USED AS... On top of that, you are missing a very important point. Namely, NO GUIDE, NO SYSTEM, can change the people playing it. Some people will want to emphasize aspect A, others will want to emphasize aspect B. The same thing goes for this hobby (and it IS a hobby, as well as a game, I think) being seen as primarily played by nerds. Well, that's because many of us DO act nerd-like around others. Even I am sometimes put off by my players constantly talking about how well de did during the latest RPG-session, or about their characters' statistics, etc. And still, most of them really ACT OUT their parts while playing! You will NEVER be able to change this, as this would mean you would have to become God and change human nature itself.
Of course, many of us AREN'T 'nerdish', but the general perception of the people at large will have to be changed by OUR OWN INDIVIDUAL ACTIONS and not by changing the name 'role-playing game' itself. I think most of us do try to promote our hobby, we bring in new people, they bring in others, etc. The only thing we can try is present this hobby as something which we don't talk about constantly... if people think we have NO LIVES because we keep yapping about our hobby, it's going to become difficult to draw them in.
Apart from that, RPG's CAN be marketed more efficiently. The problem is: it will take better marketing strategies AND more money for that... And the pool of potential players isn't THAT large, although I don't think we know how large it IS.
Shortly put: it's in our own hands, and RPG's will always be moulded according to individual tastes.