The only perfect 10 (besides MGS4) thus far this gen.
I have put more hours into this game than any other console game. It is nothing short of the hype that certainly surrounds it. The more recent Call Of Duty titles have yet to live up to COD4.
The overall game play is nothing new, it's just done perfectly. Between sniping, running and gunning, or even noob tubing, it all makes sense.
There is a wide variety of game modes that tend to cater to any sort of player. The maps are well thought out and present different elements directing for certain types of playing styles.
What made this game as well as the entire series to date, so successful, was the ranking up system. Everyone loves to gain power, that's not a secret just human nature. COD4 rewards you with new guns and power ups or perks as they're called which help promote to the multi player experience.
The single player campaign is just as well thought out. It gives a more immersive experience than some other shooters out there.