whatever your friends play. all 3 of those (well pokemon if i was like 12 again) are good buys and will be fun for a long time. iirc halo 4 is going to need a 25$ pass to get regular content --- GT: Extract Hz
Pokemon changes even less per game then Most cods. Blops 2 is finally like almost a new game. More of your friends will be playing Blops 2. Get Blops and socialize with friends rather than sitting alone by yourself playing a video game.
This isn't exactly a good place to make this topic as you'll get biased opinions. I'd say Pokemon is going to give you the most playability. Rent halo 4 and blops2 even though if you already own a cod game I don't think it's worth the update. --- Just some guy from the Internet Proud Indie Game Developer making Dubstep the videogame