There is some things to take into consideration. GTA V is on two different consoles, whereas Pokemon X and Y are on one. Also, Pokemon is a foreign game and an RPG game. It's not something as mainstream as first person shooters so many people will discard it. Even so, if you look at the whole franchise of both games, Pokemon is selling way more. Plus, Pokemon is not only appealing to young children (and directed for!), but to young adults too. Now that's saying something.