I like Call of Duty World at War better than the FIRST Modern Warfare. Besides, I tried playing CoD4 a year and a half after its release online, and I got killed a lot and World at War has funner guns.
Wait, COD5? There isn't a COD5. Do you mean WaW? Well, in that case, I'm going with MW2. I've been playing WWII games forever, and if they do add FAMAS, I'm going to "Pwn" everyone. P.S. Maybe communist zombies?
Comparing these games is like holding an apple in one hand and an orange in the other and asking people which they like better. Obviously a game in modern times will be different to back in 1945.
The only thing similar is that they are FPSs and are made by the same guys.
Modern warfare 2 looks promoising by the gameplay trailers, New guns such as the FAMAS and SPAS12 are confirmed in the video but I think modern warefare 2 will need some sort of minigame to mach zombie nazis e.g zombie terrorists or mabye something completely new?