Ourph, I would argue that what you are saying is only true if you insist that RPG's have to focus on combat. Sure, totally agree that teaching 3e or 4e combat to a complete newbie is an uphill battle. For that reason, I would never introduce new gamers to RPG's with D&D.
I think a lot of us were introduced to RPG's via D&D because, for most intents and purposes, it was the only game in town. Even games that weren't D&D, were still pretty close. Today though? There are so many indie games that would work as a much better vehicle into the hobby because they focus on the one thing that other games can't do - the shared imagination space.
First, I'm not saying the boardgames are necessarily the best introduction to the hobby at large. I'm specifically saying the board games are a good introduction to 4e.
Second, if we're talking about introducing children to RPGs, I think the one thing that an introductory game can
most do without is a focus on the "shared imagination space". Not because such a thing isn't important to RPGs (it is), but because kids already know how to do that and do it on their own all the time as a natural part of play.
The important aspects of any game (including an introductory one) are 1) giving the players some mechanics to resolve challenges that come up in the imaginary space (the board games do a great job as an introduction to mechanics like combat, healing and party cooperation) and; 2) providing a rough foundation for the imaginary space that players can build on (the board games show the players what kind of characters and creatures inhabit the world and some of the types of challenges/quests they can expect their characters to take on). The only thing the board games don't do is provide a full set of resolution mechanics. The next logical step in the progression (Essentials) does just that in a way that should be easily comprehensible to just about anyone.
Imagine the state of the hobby if most gamers were introduced into RPG's via Dread or Mouseguard or, heck, even The Secret Lives of Gingerbread Men.
There is a reason those games are "indie". They are not to the taste of the vast majority of people who play RPGs. I imagine the state of the hobby if
The Secret Lives of Gingerbread Men were the main introduction to RPG gaming would be considerably less robust than it is now.
Introduce the roleplay aspects first - all the good habits that good players have
That smells distinctly of one-true-wayism. I have no desire for every future gamer to be molded into someone else's vision of what a "good" roleplayer is. I think future gamers should be free to find out for themselves what approach to the hobby works best for them. A multitude of options is a
GOOD thing (including the combat/exploration-focused option called D&D).
emphasise things like the amateur theatrics aspect
The people who are interested in that focus are a very small subset of the RPG hobby. Why should that one thing be emphasized over all others? There is nothing wrong with enjoying the myriad other aspects of play that RPGs have to offer. The
LAST thing I think an introductory game should be doing is telling new players that there are "correct" and "incorrect" ways to have fun with RPGs.
Heck, Vampire leveraged the whole amateur theatrics thing into what stood as the second biggest (and for a short time biggest) RPG line for a long time. There's no reason D&D can't go a similar route.
No, Vampire leveraged 90's goth culture and the fascination with moody, angsty, bodice-ripping, over-romanticized vampires into the second biggest RPG line at the time (a time, I might add, when TSR was self-destructing through application of horrific management practices, i.e. not putting up much of a fight

). And yes, D&D could go a similar route, but why should it? Are you suggesting there is no need or desire for an action/adventure-oriented fantasy roleplaying game like D&D in the hobby? I've never understood why people seem to think that D&D needs to become just like their favorite RPG. If you want to play Vampire, why not just
play Vampire and let the fans of D&D enjoy their game of choice too?