Should I get Fallout 3 or Fable II?

So I want to get one of these RPG's for Christmas. I have never owned a legit RPG before (unless you count Pokemon) and I am looking to expand my videogame library from Call of Duty, GTA, and Rock Band. I borrowed Oblivion from my friend and gave it back to him the next day, I hated it. So at first I thought Fable was out of the question because I disliked Oblivion. But then my other friend, who hated Oblivion also, LOVES Fable. Also, I thought I would get Fallout, because I have always liked guns more than magic. But now I've heard a lot of bad things about Fallout about how the combat is too easy and always the same, and there aren't a lot of creatures to fight against. And I want a game that has a lasting appeal and that once I get it, I will want to do it again and again and again. Which game do you think I should get?