Let me start by stating something important, which is that Crysis 2 is an excellent game and worth playing if you have ever enjoyed first-person shooters (FPS) at all. The core design is very strong, especially the extent to which the nanosuit was tuned to make the player feel like a badass without feeling invulnerable. On many levels, however, I thought the game couldn't really decide what it wanted to be about. Is it a game about making sound tactical choices in an operation against a superior force, or is it a (bad) story about squid attacking New York City with a bio-weapon?
It's clear that Crysis 2 wants players to take its story seriously, though its B-movie schlock hardly warrants the attention. The audible suffering and grotesquerie of the infected civilians is obviously intended to evoke the player's sympathy, and the concept of a devastating attack on New York City is an obvious, if feeble, attempt to provide gravity for the narrative.
Beyond this, the game consistently overrides or ignores player input in the interest of furthering its story. The main character, Alcatraz, holsters his gun at several points in the game, as a way of (partially) preventing player actions from interfering with the game's presentation. Additionally, there are several moments where "suit malfunctions" wrest all or most of the player's control away. The levels are essentially inert—although the buildings crumple like paper when the designers demand it, they do not respond dynamically during the course of play, else that big glass window at Hargreave-Rasch would have shattered from all those freely-fired HMG rounds and grenades.
Much of this is conventional, but Crysis 2 goes further, adopting many of the characteristics of cinematic action games, most particularly the attempt to disguise conspicuously game-like elements within the fiction. You can see this in the use of the finger display for suit upgrades, and the modification display for the guns. It is also evident in the save system. Checkpoint saves achieve two ends that are desirable for the cinematic style. They remove a layer of menus, thus disguising software elements, and they privilege narrative flow over player input, by removing the ability to play freely without progressing the story.
This also tilts the gameplay against improvisation, an interesting choice since one of the game's strengths is the flexibility of the nanosuit's various abilities. The game's core loop is appraise-execute-rearm, in many cases reinforced by an arena-chokepoint-arena architecture. Tactical failure is punished severely by heavy reinforcement, a special burden for stealth-focused players, and often results in a messy death. This kicks the player back to the appraisal step. Without the ability to save or reset partway through an arena (e.g. Far Cry 2's buddy system), this construction encourages the player to focus on planning rather than experimentation. In this regard, the ready-made strategies offered by the tactical display shift even the core gameplay to the developer's hand, although in most levels additional approaches can also succeed.
Yet, there are also many ways in which Crysis 2 is not serious about its story, and not only in the conceptual vacuity of its imagined alien invasion. Nearly every plot development, and most of the objectives, barely make sense even in context, and there's not much nice to say about inventing a race of vicious alien squid only to have them scamper around on dry land in bipedal exosuits. Aside from simply failing to provide any ideas worth taking seriously, Crysis 2 also suffers from an inconsistent effort to make the player take it that way.
The easy complaint is that the collectibles are at odds with the storytelling. Certainly the idea that a marine in desperate straits will think to grab a souvenir tchotchke off an office desk in the middle of an alien invasion, much less poke around for car keys, is relentlessly silly. That these items so often lie off the main path makes them particularly disruptive. The e-mail downloads are less troublesome, however, and with some tweaks to the implementation, the dog-tags could have actually been a moving part of the character arc, if Alcatraz had been a character or had an arc.
Collecting dog tags from fallen comrades might have at least built being a Marine (as opposed to just being a guy with a gun) into the gameplay. Alcatraz's silence, however, would undermine any effort to construct him through procedure. His failure to ever verbally acknowledge an order fights his characterization as a Marine, and that he never asks obvious questions makes him seem like he's not much of a human being. Alcatraz isn't an everyman, he's a no-man, and his position as a silent protagonist makes the game show through the cinematic seams of the fiction.
This happens in other ways too, few more conspicuous than a battle against a helicopter in Nathan Gould's lab. In the final phase of this fight, the lab is bombarded by rockets from the helicopter, yet the explosions do no structural damage. What's more, as the copter itself can only be taken down by a rocket, the game supplies them by having of soldiers armed with rockets (why?) jump into the room as it is being bombarded. As gameplay this is perfectly conventional—the FPS equivalent of the bomb flowers in King Dodongo's cavern—but as fiction it is transparently ludicrous.
None of this "ruins the game" for me, nor should it for anyone else. But as I played Crysis 2 I was continually perplexed by my lack of enthusiasm for it, despite the fact that I found the gameplay fun and engaging. What dragged the experience down for me was the manner of its construction, which was guided by an insistence that I pay attention to and engage with a schlock narrative that was, frankly, beneath consideration. The frustration was only magnified by the moments that showed me the game wasn't taking its story as seriously as it was trying to make me do. I was happiest with Crysis 2 when it shut up and let me do awesome things with the nanosuit. Hopefully, the third game will focus more on that and less on the worthless story.