Well, this is quite old, but the first game that I ever got was the one that came along with the Xbox which was GTA V, I really saved up for a while in order to buy this bundle, it's amazing though.
Old thread, however, my first Xbox One games were Forza Motorsport 5, followed by Call of Duty - Ghost, then GTA V. 2013 in my opinion, was such a good year for gaming in general!
This brings back so many memories since we're in 2017 now. I still remember buying my Xbox One though, I was so excited. The very first game I've bought for it was Watch Dogs and then GTA V when it was released.
Those two games are still one of my top ones. I enjoyed them so, so much. I still play GTA V online all the time. It's quite easy to find more things to do since Rockstar Games are adding so much free DLC.