What makes a truly great action movie? It's a desperate John McClane jamming some C4 beneath a monitor and experimentally kicking it down a lift shaft on a swivel chair. It's Indy telling Sallah "I don't know, I'm making this up as I go" before instinctively tearing after a Nazi truck.
It's all about a hero living on his wits, making life or death decisions on the fly and the world hinging on his actions. Crysis encapsulates this, it thrives on putting the onus on you to create your own brand of action and adventure in its stunningly beautiful locations. You and the game can haphazardly create moments of such gaming brilliance that often you pretty much have to stand up and applaud.