The story is generic, but gameplay wise it is one of (if not the) best fps games to date. Warhead is slightly more generic, but still much better than Crysis2 and 3 in gamplay quality.
I feel that all four games succeeded in their own way in terms of gameplay. Warhead didn't have quite the highs of Crysis, but I felt Warhead was a much more even experience from beginning to end and it fixed a lot of the problems Crysis had in terms of fighting the aliens. Warhead is probably my favorite Crysis campaign. Plus, Crysis Wars is still one of the most fun multiplayer experiences I've had since Quake 3. 2, I felt, handled the idea of combat freedom a bit better than Crysis 1. They stripped way too many suit abilities and the game itself had other problems, but I liked a lot of the combat arenas in the game. I like 3 as well. Its a nice mix of what worked in Crysis 1 and what worked in 3. All four games really nailed the gun play.