I went with Grand Theft Auto V. It is currently releasing on only two platforms which should help focus sales. The last title sold over 10 million on the 360 and over 9 million on the PS3. The franchise is incredibly popular in North America and has already managed to get well over 300,000 pre-orders for the 360 and PS3 each in the United States alone.
I considered Gran Turismo 6 but based on the mild disappointment many felt for the last title I have a feeling it won't do as well as its predecessor. Call of Duty: Ghosts and Battlefield 4 would have been considered were it not for the fact that they will have next-gen versions at roughly the same time as their current-gen versions. I'm fairly certain that will seriously impact the sales of all individual versions. For the 360, both titles currently have less than half the pre-orders of Grand Theft Auto V. I also feel that the Call of Duty franchise is going to begin a serious decline.
Both Pokemon X/Y and The Last of Us could very well outsell the others. Pokemon is a very popular franchise and the 3DS is currently the best selling gaming platform. The Last of Us has already sold several million copies and while it will certainly slow down over the Summer it will be interesting to see if it picks back up during the holidays. It already has a good lead heading into the second half of the year. That lead could prove the difference by the end of the year but I'm banking on the huge appeal of GTA in North America and the currently much lower install base of the 3DS (compared to PS3 and 360) to be the reason why Pokemon X/Y and The Last of Us don't win.
EDIT: I feel I should note that when I say the 3DS is currently the best selling I mean that it is currently selling better week-to-week than all other platforms. NOT that it has sold more overall. I know some people will want to jump me for that.
