Im mostly a fan of open world games, and so far the the majority of games i have that are the best examples of this are Elder scrolls games and current Fallout incarnation, i prefer Fallout 3 over Skyrim because i think Skyrim just lacked real story background and quests, after awhile it seemed like you were just running around for no real reason, but i had endless enjoyment climbing mountains and looking at the beautiful scenery, watching the fish jump in the rivers, sometimes the little things can make a game.
Fallout 3 i enjoyed more because of all the places you could go and piece a jigsaw together of a world before the destruction, the major disappointment was the areas sealed off by rubble, would have loved to wandered into more buildings and more streets in the DC wasteland.