Spoilers.
Crysis Rundown:
The first 80% of the game is pure, unfiltered brilliance. Everything up to your entrance into the core was gold, once you come to terms with switching your suits abilities quickly (suit shortcuts on FTW), and very atmospheric to boot, no doubt thanks to the best-in-class graphics and physics.
The core itself was awesome in its own way. The Zero G twist and new visual environment were very nice and wonderous...the little touches, like icicles floating when you shot/broke them off was nice. I didn't mind the linearity in this portion - it makes sense in context - but my character talking to himself was way too obvious of a way to cue the player in on what he/she was supposed to do.
The aliens themselves were mediocre. I already saw the Matrix.
Upon emergence from the core, I love what they did with the environment, not so much the gameplay. We're back outside now. It's supposed to be back to open ended craziness, but instead it's a linear escort mission. I would've been ok with that if they'd turned me loose after getting Prophet to safety, preferably sending me back in the sphere for a few missions to goof off in the frozen environs. No such luck.
The VTOL piloting sequence would've been fun if the thing didn't handle like a wet turd tied to a helium balloon. Yahtzee got it right - like trying to solve a rubix cube with your elbows. I didn't shoot down any more aliens than absolutely necessary until I could make a run for the carrier, then just juked and dodged the fire until I got the level change.
The carrier started fun and turned stupid. The initial defense of the flight deck and core shutdown was fun. The Alien Exosuit (which I thought was the boss) was just annoying. I'm with Imp - we couldn't stop it with a bunch of RPGs, AA Guns/missiles, and a full platoon of troops on land, and then I manage to take it out on the flight deck by sitting behind a crate and popping out to plink it in the forehead with the Gauss Rifle about 13495002 times over the course of a 1/3 hour, and eventually killing the thing on accident. If you're going to have something play the part of Unstoppable Death Engine, there needs to be some trick to taking it out.
The *real* final boss was just sad. Shoot parts A, B, C, fire your special Bigass Gun up its anus, then run. Also, deal with piddly Regular Aliens while trying to take care of this business. Not impressive.
Overall, I'd say Crytek made about 85% of a screamingly brilliant game. The stuff near the end that stinks, it stinks of "we've got a ship-date to make and we need an ending". I think if they'd let this game cook for another year, two wonderful things would've happened:
1) We'd have a proper ending.
2) There would be hardware out that could actually run the damn game.
Bonus Gripe:
The "air strike" sequences annoyed the hell out of me. It's 2020, and we have F-22/35s dropping BLIND DEADFALL BOMBS from 50 feet above their targets! We don't use that shit NOW in 2008. If I'm calling in an airstrike in a modern game, any modern game, I should paint the target for a few seconds and then all of a sudden see the warhead come screaming in almost too fast to see and then my target disappears inside an explosion of substance. Bombs come from technological marvels at 30,000 feet, not from technological marvels within handgun-range of the target.