Yep me too Mael, I always liked to play the SP in the COD games. Honestly, I think most people believe that COD4 will always be the best SP of the entire "new age" series (i.e. not including COD1 and COD2 here. COD2 might take the cake for best overall?), but MW1 and MW2 were also AWESOME single player. MW3 lost me a little bit, as did Ghosts. Wasn't into the SP story as much in those releasses but it was still fun, just because FPS dynamics are fun when done right.
I haven't tried Black Ops 2, but if I did try BO2 and BO3, it would probably be for the single player.
Besides Battlefield, I don't think I'll be playing too many FPS games until some sort of -TRUE QUAKE KILLER- comes out.