I have to confess I was taken in by all the hype, thus deciding to invest in this recently & I can honestly state that (IMHO) the online mode simply does not make this a great game. The Campaign mode is ok, but the sum being more than the parts, COD4 is not a 5* game in any sense of the word. A rather large FACT all too often overlooked is that the MAJORITY of gamers DO NOT play online. So realistically, ANY game should be judged by it's online & OFFLINE modes.
It may just be that I've missed something along the way (if you know, please educate me) , but this is far from the 'best game ever'. The graphics are ok [better than Haze ;-) ], but far from awesome. However, the games audio is close to excellent.
To be fair, I really have tried to 'love' this game, but at every turn I fail to see what all the hype is about? However, it's evident proof that it can & does overwhelm the majority of the gaming populace. Thankfully, gaming is not a democracy ;-p