Messed it all up? This is what cod was originally about people. Both modern combat and world at war play very similiar to me. There are a few differences, but hey guess what, theyre made by different people.
Im tired of this back and forth though. If you liked modern combat, wait for cod 6(fall 2009). Infinity Ward will have the game again and i hear its going to be modern again(by modern i mean sci-fi).
In terms of graphics both games are the same. Gameplay wise, the levels are obviously way different(60 yrs difference of timeline maybe), but they both use the same exact engine. Knowing that they use the same engine should squash all this talk about crappy graphics and subpar controls. THEY ARE THE SAME. Multiplayer, i will concede to cod 4 being the winner of this category(more weapons, etc). Other than these things what is there to gripe about?