what i liked a lot about skyrim and I think made the world alive is the fact that npcs had their own routines, they did not stay put in one place for all eternity, they moved depending on the time of the day and even depending on the day of the week. this way day and night actually made a difference in gameplay. I dont know to what extend it copuld be possible to do something like that in here. also if animals could be more animals it would be great. in most mmorpgs i know, wild beasts roam mindlesly like zombies without any purpose... that also takes away some feeling of a "living" environment

Predictability can grow stale in mmo's

That was also a big point many years ago in Gothic and Gothic 2. These simple NPC Routines like sitting in front of his house, then, later, washing some dishes in the river, sitting on a table in his house an going to bed till the next morning made the whole world so alive. Also i liked in the gothic games, that NPCs showed little Reactions to players behavior. For example, when you draw a weapon in a city, some guards yelled: "put that thing away" while some of the citizens stand close and cheered for a fight. Also, they reacted, when a player entered their house. Some things like: "Who are you, get out of my house, i call for the guards..." 
Small things like this let a player forget, that they are only NPCs. Some of them grow to remembered Charakters, even when they never had a Quest for you or have been important for the story...