weirdness of the setting and the feeling of getting lost in a strange land
Morrowind had a certain "what if we threw every fantasy trope at the wall and see what sticks" angle than a lot of games. That required a significant amount of art direction to pull off. But, even setting aside AI, we've made huge progress in modeling and skinning assets. I don't think we're going to stop seeing games with dozens of class/race pairings any time soon.