Crysis 1, then warhead then 2.
Im not sure if it was because i was too used to both crysis and crysis warhead, but i simply didnt enjoy crysis 2 at all (neve finished the game, ended up about 40% on the way).
For me crysis 2 was a call of duty with nanosuit and a make up on graphics.
I know most people wont agree with me, but thats just my opinion.
Crysis 1 still impresses me (thou its showing its ge by now), and im very sad that crytek abandoned Nomad and his story, as well as crysis form of gameplay.
I just wanted to go back to that island and wreck havok among the alines (it would actually be amazing if at some point you had to go to new york to continue your adventure, but not start a whole new story there...).
Another thing is that in crysis 1, when the final boss shows up.... that thing is huge, and the graphics are good enought to back it up. You actually get the feling that the damn thing is monstrous.
On the Warhead side, the als boss looked very small in comparison, and in crysis 2... well i never got to the end but i heard there is no boss?
Both crysis 1 and 2 have great visuals, but i feel like some of the crysis 2 technologies are just not there (particle system for destroyed objects? volumetric smoke? physx? I dont know, jsut felt like they were not there.)
On the other hand, crysis 1 had some bad coding
.