I'm going with the Fallout series, just cause there's so much shit you can do. And it never gets boring.
Fable 1 was an amazing game. Fable 2 and 3 sucked, just wasn't the same. TES > fallout in my opinion. They both have incredibly distinctive feels to them but I just like TES better. I always feel like their's more to discover in the elder scrolls universe, it never gives you a full view of the world and retains the medieval ignorance of that type of time period. Since each game is restricted to a province you experience very distinct cultures and there is virtually limitless lore. Fallouts lore equates to bombs dropped, we stayed in the 50's for a bazillion years. Now we live in a wasteland.
The Legend of Zelda. I wish I still had a Wii so I could play the awesomeness that will be Skyward Sword.