I think the actual shooting and feel of the action in Call of Duty 4 is pretty poor. The weapons are indistinct and don't have any sense of impact. Save for incredibly minor differences in accuracy and rate of fire, for example, all machine guns are more or less the same, as are sniper rifles, pistols, etc. I prefer a "less is more" approach to shooters when it comes to weaponry - Half-Life 2 still stands unparalleled as having awesome-feeling weapons that are all unique both in feel and application. Far Cry 2 also does a much better job of creating weapons with a real sense of personality to them, even if they're a bit less realistic.
Nah, where the game's strength really lies is in its pacing and presentation. I still go back to play the single-player despite the fact that I've beaten it several times over, partially because it's easy to pick up and play, and partially because it's fun to look at, providing a very nice ratio of calm to chaos. I can think of way more titles that do the core combat much better, though. The chaos of war is definitely a strength Call of Duty as a series captures well, but it really comes up lacking in artificial intelligence, variety of gameplay, etc. When I want something a bit more entertaining, I'd much rather play something like Crysis, which allows me to play at whatever speed I want, adapting to both styles of play dynamically and perfectly - either extremely slow-going and stealthy, basking in the ambiance and atmosphere of the environment, or blowing everything to bits with explosives.
