This is one of the best FPS titles to come out in the last ten years or so.
While the storyline for Crysis wasn't exactly a work of art, what made this game such a masterpiece is its impressive graphics (which still look good today), open-world environment, and extremely versatile gameplay. Your combat suit offers a smorgasbord of ways to fight, as does various attachments you can get for your weapons.
Other than a few limitations in the game, just about anything you wanted to do in the game, you could do.
Up until recently, Crysis was a PC exclusive that required an extremely powerful computer to run it, but now I believe you can get this game digitally for the Xbox 360 and PS3.