For me it's the greatest video game ever made. 8 years on and It's still light years ahead of it's nearest competitor.
The A.I in this game is just incredible. Every soldier under your command will follow orders without question - order them to drive a Jeep to the other side of the island, get out, jump into a gunship and fly to your location and rain down fire on the enemy, then land get out and salute you and they will do exactly that!!
A convoy of trucks will follow the roads and weave between buildings as if driven by real players....Medics will come to your aid when you're wounded...enemy soldiers drop down to the ground when fired upon...the list goes on and on.
It's simply the most immersive gaming experience ever crafted by man.