IMHO, a role playing game, is a game in which you play a specific role of your choosing in the provided environment, this role can be a fixed one selected from the few provided, or an open and mold-able one that you develop gradually over time.
Role playing as defined in game series like the Elderscrolls, is gradually developing your role in an open world that let you freely choose your actions as you like, but on the other hand, you should be able to feel and enjoy the development of your character, and have small and large triumphs over previously unbeatable problems and obstacles, and that's how your character should seem developing.
Another aspect of role playing games, is the role that you choose to play, so each character should feel unique and special, so it is better that all your character should seem individually different from the other characters, even until the final stages of the game when your characters have fully grown.
Those are the parameters that I appreciate in a role playing game, and they can be achieved by visible stats to be increased, or by other means, like choosing perks, and so on...
So to sum it up, in an Elderscrolls open world role playing game, I want to role play a specific, unique and distinct type of character, that feels different from when I choose another type of role in the world, and develop it gradually over time, so that in the beginning I should be bound and limited by natural barriers like, insufficient skills or dangerous places and the like which I should be able to overcome as I gradually develop my character.
The new introduction of pick-able skill perk tree is that you would not be able to pick up completely to the end is a sure way to make unique characters with, and is a great game design decision.
If the keep their promise and return to Morrowind standards, and make it hard to join and advance in guilds, and some places would be hard to venture into at the beginning, so that we could feel the sense of progression as we develop our character, then IMHO Skyrim will be a much better RPG because it would provide me with what I value in an RPG game, and more than the previous games.