So call me old fashioned but when I go about my day I expect people to actually speak to me. The fact that NPCs don't even murmur something when you click on them, let alone say anything at all, kind of makes the world feel lifeless.
And, while I'm at it, have you ever noticed that monsters don't even complain when you kill them. They just stand there and maybe fall onto their back or curl up into a ball every so often (which are nice touches, I don't deny). But the point is, they barely exhibit any kind of expressive behaviour.
There really needs to be more vocalisation. If it's too much to ask to have important quests voiced, then at least just give the NPCs a few words to say. You know, here and there. And the mobs too, they need to be more expressive.