Currently it's BF4. I had a lot of fun with the Black Ops series last gen, along with Halo as well. I didn't really "get" Halo until last gen, but that game can be a ton of fun once you kind of figure it out and play with friends. Black Ops, to me, had the best mix of the Call of Duty games, and that game was a blast.
I didn't really get into shooters to any competitive degree outside of Perfect Dark and Goldeneye with friends until the PS3/360 era.