TheLastStarFighter on 19 May 2013
Absolute, far and away best exploration I've experienced is Xenoblade. Bizarre, beautiful open world. You are rewarded for exploration. What truly makes it extra good though, is that the whole world is connected, and what you see in the distance can be eventually reached and explored as well. There is no "background. And the strange nature of the world makes you want to see it from every angle just to try to grasp the enormity of it all.
