Building an RPG in this day and age is a bit more tricky than it was a few years ago. You need a deep story and alternate paths to make the game interesting and allow characters to evolve through a player's decision. BioWare's Greg Zeschuk recently spoke with Gamasutra about BioWare's design process for games like Dragon Age: Origins and his role in the Mythic/BioWare merger.
The interesting thing is that even as big as the game is, with the way you get so engaged with it, when you miss something, you almost feel like you've gotta do it over again. One thing we did in Dragon Age is that you can't see everything in one playthrough. It's impossible, literally impossible. Depending how you design your character and what things you value and don't value, certain quests are going to work and some won't work. There are a lot of quests you just can't do.