^ still adding more stuff to the list.
NPCs in FO3,
- have their own schedules, and are doing different stuff depending on the time of day.
- can seamlessly roam the Wasteland on their own, and you can follow them.
- will comment on whatever you're looking at: "Yes, that's locked, and yes; I can see you eyeing it."
- will refer to the fact that you've been going around asking other NPCs the same things, when you bring it up with them.
- will mention other NPCs, including their absence. i.e. after Simms or Moriarty have died, they'll be referred to in the past tense.
- will mention the events you've taken part it.
- will behave differently depending on how Good or Evil you've been.
amongst other things.
- All equipment doesn't fit you.
and yet Sten can wear the same armor as Oghren or Leliana does.
- Thedas doesn't exist, Washington already does. They just blew it up.
Thedas already exists and it's called Middle Earth, or Faerun, or the Old World, or any other Western Medieval Fantasy setting. They just changed the names and roles a bit (an unfortunate exaggeration, but you get the point.)
Party members and codex make half the game. You just can't get rid of them.
There you go then. Those make up more than half of the game actually; without these it would be little more than a generic Tolkienesque WRPG wrapped around a bedtime story, as it were, whereas FO3 has way more numerous elements coming together to build a more solid experience, IMO.