giant.robot
Adventurer
Let me turn it around. What would a basic D&D game teach potential new players that they cannot learn from a host of other sources?
I think this is one of the better points made in the thread (no offense to anyone else). A player that is new to pen and paper RPGs in 2011 likely has way more experience with RPGs than their 1981 counterpart. It's unlikely that they haven't played some CRPG or CCG before picking up a D&D book. An RPG rule book printed today doesn't need to spend a whole chapter explaining the concept of role playing games.
However I think there's definitely a place for a "Basic Game". I'm in partial agreement with Mercurius about the design of "21st century" games. Even if the core concepts of the "21st century" games are relatively simple they kind of throw new players into the deep end. There's no shallow end of the D&D pool anymore. The new Red Box and the rest of Essentials go half way there but I still feel they are a lot for new players to handle. A "Basic Game" isn't so much about teaching players about RPGs in general but teaching them pen and paper D&D specifically.
I think the Red Box rules should have started with the absolute D&D basics closer to the Microlite20 rules. Players could choose from three classes: Fighter, Cleric, and Mage. They would only have three ability scores (STR, DEX, INT), low HP (Fighter 6, Cleric 5, Mage 4), and a single defense value with a slight bonus if they can wear armor. Each class would only have two powers (probably an attack and utility) that would do enough damage to kill a minion but take a few successful hits to beat a bigger monster. Most of the monsters would be minions with attacks on them just keying off of ability scores. Traps and the like would also just use ability modifiers.
This would have put the scale of the game much closer to that of the Mentzer Red Box but also provide an introduction to the mechanics of the game without overwhelming new players. When they decide they want more options they can pick up Heroes of the Forgotten Lands and build a full character with all of the options. The "Basic Game" is forward compatible with the full game but doesn't throw new players in the deep end.
I think part of the attraction of many of the OSR games is they have rules that are easy to explain to new players. You get the open ended and free-form nature of an RPG without the sprawling list of rules. I've introduced a lot of people to RPGs over the years and something almost universal is the fear in people's eyes when you pull out a rulebook the size of a college textbook. It's hard to convince someone the game is actually fun when it looks like you're giving them a thesis paper to write. It doesn't help that the character sheets look like IRS forms.
A "Basic Game" would get people familiar with the absolute core concepts of the game and sitting down with some friends and playing. They then get to add complexity at their own pace rather than at whatever pace the game designers thought was appropriate.