If you look at the spectrum of popular RPGs we are blessed with they all take a different approach towards their game-play and design.
The Elder Scroll series in particular stands out as an RPG series that defines itself via the openness, vastness and detail of it's world. In fact, the world is often the focal point of the whole game where as the narrative is often just an afterthought. Most of the player enjoyment comes from exploring and building their character builds.
There used to be much more of these "open world" RPGs but TES series is by far the most popular.
Now on the other extreme we have very "driven" RPGs who's main focus is on telling an epic tail with relate-able characters and lots of drama. In a way they try to be as cinematic as possible. Popular examples would include the Mass Effect series and the Witcher 2.
Now these are just extremes I'm talking about. Obviously all RPGs contain an element of exploration and character building but to very different degrees.
Now, the actual quality of the product aside, what type of RPGs do you generally favor? The more "open world" one's or the more "driven" one's, each with their respective Strengths and Weaknesses.
Edit: This is about RPGs, not MMO's. Damn you brain!