You know, last year I taught a group of 12 year olds the basics of BRP (Magic World, specifically) and got in a full one-shot in one evenings' play. These kids had been playing Blue Rose. I find BRP very easy to teach. Also to complete novices, as it was the 'entry drug' for my wife, the game I got her to try. Why? Because she picked up the concepts quickly, which she definitely did not when I tried teaching her 2e AD&D a year earlier. Nope, it may not be as simple mechanically as Prince Valiant and such, but it is still a breeze to teach others or learn. Really.
