A common misconception:
Modern Warfare > World at War < Modern Warfare 2
Or Modern Warfare < World at War > Modern Warfare 2
In all actuality, though, this is how it goes:
Modern Warfare ≅ World at War ≅ Modern Warfare 2
None of these games are better than each other, and it is as simple as that. We all have our own preferences, as all human beings do, but there are no facts that make any one of these games better than the other. Each have their pros, and each have their cons. To say World at War sucks is to say Modern Warfare sucked, due to the similarity between the two games. Perhaps Treyarch should have gotten more creative, but all the same, it is very similar to its predecessor, and therefore should not be looked down upon.
Modern Warfare 2 took a chance, and implemented many new things into the Call of Duty franchise. Titles and emblems, and customizable kill streaks, Modern Warfare 2 gave us creative freedom like never before. Was the system flawless? Certainly not, it had, and still has many issues to this day.
My point in this is that to say any one of these games are better than the other is mere opinion, no facts. Trashing Infinity Ward or Treyarch is simply a waste of time, as neither of the two are better than the others indefinitely. I think we all should give Treyarch a chance to shine with this title, instead of dismissing it based on some early trailers of the game. The game still has a long way to go, and despite the developer, it could be a great game.