I'm surprised nobody has mentioned Everquest Next/Landmark. SOE-hate aside, it looks a solid AAA attempt at a true sandbox MMO. Check out the dev diaries...I gotta say, it looks like it has potential. And if it fails, we may not ever see another big budget sandbox MMO for a long, long time.
It sure look like it has potential, but holding up a game as an example that is not yet even in Beta is not a great idea.