I'm a big fan of easy D&D, which means, for me, two things: "easy for the dm to prep" and "easy to explain to a first-time player".
For me, the ideal prep for a game involves brainstorming a few characters and gimmicks. My DM notes generally look like this: "whenever the PCs search a house, they have a 1 in 3 chance of finding the black-handled knife. Whoever owns the house is the witch." and I never get around to looking up the Night Hag stat block.
I've also played a lot of D&D with first-time players, and the more rules they need to learn before they start playing, the more ashamed I feel for wasting their time. I think the ideal situation for a new player is to choose between a few pregens of recognizable archetypes, each of which has a couple of cool, simple attacks.
Experienced players should have lots of customization options, but experienced players can look after their damn selves.
I've been trying a playtest version of Jason Hurst's d4 Basic game. It's sort of a D&D-style RPG/board game which takes the "easiest" elements from each. From the RPG corner, it keeps the idea of the game master who makes judgment calls and referees actions outside the rules. From the Descent-style board game corner, it uses pregen characters and scenarios, clockwise play, and win conditions. The result is a rpg manual that's about 7 pages long: and actually, when you subtract art, table of contents, and the usual "what is an RPG and "what are dice" sections, it's probably 3 or 4 pages of rules. There's more text in the scenarios, treasure cards, and so on, but it's still probably 1/4 of the length of the Descent rules and a tiny fraction of the length of any D&D edition. You could play it with zero prep, and you could probably have a RPG n00b run the thing.
D4 Basic is in open beta right now.