Honestly, in the last couple of weeks, I got Skyrim, Assassin's Creed: Revelations, and Saint's Row: The Third. And in a couple of days, my copy of Skyward Sword is going to be arriving. As it is though, as much as I am enjoying all three, soon to be four games (and if we're counting the games I also got in October, SIX), The Third has been easily getting the most playtime from me.
I suppose it's just the immediate payoff that is appealing to me right now. Rather than trying to get outside of Whiterun only to be sacked by bears constantly (granted, because I'm being impatient), or having to re-learn the play mechanics in AC:R (same thing happened when I played Brotherhood), I'm just enjoying being able to jump right into a game that I know exactly the scope of it, and just screwing around.
And for those who still draw the GTA rip-off card: Just. Stop. It's like trying to say how "The Naked Gun" is a rip-off of "Dirty Harry."