Crysis puts you in the shoes of a special squad sent to investigate a distress call on North Korean islands and quickly jumps into combat mode. The Nano suit equipped with special powers & effects like invisibility cloak, strength mode (which allows you to make higher jumps & powerful melee), speed burst, extra armor etc makes the game very innovative. You can have different approach to tactical situations and opt for stealth mode or blast your way out or into an enemy zone.
The AI is generally very good & they spot you from far off pretty easily and investigate in groups. They are particularly reactive to situations like when you throw a frag grenade towards a group of a single enemy soldier the scatter and disperse almost effectively from the range of grenade and do not stand there to shoot at you. The story line is average at best but what makes this one stand out are the astonishing graphics that makes the place come alive.
Midway through the game when the aliens take center stage, that is when the real fun starts & the game tends to pose a good challenge. The aliens are aggressive & come in swarms. Your weapons are effective nonetheless. Ammo & weapons are scattered throughout the game with no difficulty at all. You also end up fighting in vehicles & against them.
The only disappointing part was the end boss fight which I thought was way too easy. Couple of missions with the raptor team squad are also decent enough, but it will be you who will be doing most of the work.