I have to say, after MW2, the whole COD experience for me went south.  While I respect them as a series of games, Treyarch just didn't do it for me.  As for campaigns, I believe Battlefield had the better campaign mainly because it started to bring a whole new outlook on the first person shooter and the destruction one could make thanks to the frostbite software.  
Have you looked into BF4? The whole experience is fantastic!  Take a bit of time to get use to the chances from BF3, but it is well worth it, a solid investment if you ask me!  And the campaign is just amazing!