I really hope its Red Dead Redemption GOTY edition and Black Ops 1 because everyone thats played them loves them and you know it. And just because you may have it doesn't mean everyone else does. So I really hope its those two!!
Everybody is entitled to have a choice in what they want, but nobody knows yet. You'll have to wait until it's closer to the end of the month to find out. RDR is a good shout though, would prefer one of the Fallout games.
I'm thinking it MAY be Gears of War 2 or 3. Obviously Epic is going to bring a new Gears on the X1, this would be a good way to build up more of a fanbase. I don't really care for GoW, except the first Gears, that game was great.