Game of the Year? Game of all time?
To compare it with Halo 3, i would say it is better in every way, shape and form. There are twice as many levels in COD4 and they are all twice as exciting and fun. All the achievements are for Offline play which is great for all those without Xbox Live, but I little disapointing for us Online Gamers. Now to the online mode. Online Call of Duty is top notch, you battle with gamers from across the world and it never seems to get boring (where as in Halo 3 you get bored) every rank is attainable though. If you play call of duty a lot you would choose to prestige once you reach rank 55 where as if you don't you would sit at that rank.
Call of Duty is one of the worlds most recognised games and prior to release there was no hype compared to that of Halo 3 and GTA IV. COD4 in my opinion beats them every day of the week. So I would say it was the best game ever!