This past weekend I played in a massive, six-player game of LEGO Heroica that combined three different sets into a single playing area. Three of the players were children and three adults.
Mind you, it's a kids' game, so randomness is to be expected. Still, every time I play this game I keep thinking how easy it'd be to create an "advanced" version that is just a step or two removed from a real RPG. In my opinion, if WotC's serious about improving the lot of D&D in the mass market, they ought to be looking at games like Heroica to lay the foundation. Seriously. There's every other kind of LEGO these days. Why not Dungeons & Dragons?