Treyarch just builds on what IW does. IW is the driving force behind the series. Other than zombies all the thing Treyarch "added" were taken away remember the interactive control gimmick from COD 3? How about the ridiculously overpowered tanks in multiplayer? Or even Co-op campaign (though I liked that).
http://www.youtube.com/watch?v=F1gWECYYOSo
Please Watch/Share this video so it gets shown in Hollywood.