I have played my fair share of MMOs, and the game I spent the most time exploring the world was LOTRO. (lord of the rings online) It has been 5 or so years since I played, so not sure if it is still the same, but back then they had some deeds system where each region had challenges to kill a certain amount of creatures or explore different locations and would reward you with permanent stat boosts. I remember our guild would have nights where we would group up and tackle these challenges together, those are some of my favourite memories in gaming. Sigh, growing up sucks.