Variety, different things to find and try out. Creating a story in your head based on the world around you.
It doesn't have to be open world, exploration in half-life 2 and Ico was great as well.
It's better if it's not packed full with activities and things to find, exploring the vast near empty world of SotC was awesome, as well as exploration in Journey and sailing the seas in Wind waker. Give me some room to travel.
Once in a while a game comes along that is the perfect marriage of open world, corridor exploration, variety and story telling through world design: Dark souls.







