I would personally get Black Ops 2, but you should get saints row if you like the Free Roam side of gaming more than just running around in multiplier matches with no real objective other than killing other players.
I like Saints a lot. I played for a very long time and always had a good time. Black Ops 2 was... an alright game but depending on the person it gets boring. If you tend to quit on 1st person shooters then I feel you will lose interest on the game. If you do not like the camera angles or dynamics of a 3rd person sand box game then don't get Saints. But either game you can not go wrong with. Both pretty amazing but I would honestly, just from my point of view, recommend getting Saints Row the Third.