WoW pre-Cataclysm really did do its world well. Everywhere was pretty memorable and unique, and it was pretty easy to learn the map.

On the other hand, there is Just Cause 2 which has a huge map that I definitely don't have memorized despite all the hours I've put into that game. I don't mind that though. It's silly fun, and there's a certain joy that comes with grapplechuting around the world to not only randomly come across weird things you haven't seen before but to also stumble upon a familiar place again with fun things to grapple and blow up. I did manage to memorize all of the airports though. That was important for grappling cars to planes and watching the ensuing hilarity.

I've not given much thought on this subject. The Jimquisition episode reminds me that I need to play Resident Evil, though.