I wonder, when you have to introduce someone to DnD (especially over the internet) have you ever tried... showing them a Dead Ale Wives video? Just so that they can see some of the elements so when you explain what a DM is they already have an image?
Umm, probably not the ideal option, but I guess it works.
Maybe that paragon-tier 4e video podcast (I forgot where to find it) .. despite poor rolling, a few rules errors, and suboptimal tactics, it's a decent showcase for D&D.