Some odd glitches, but a fun game nevertheless.

A game of two parts.

COD4 - the latest and arguably best installment of the Call Of Duty series, is a proper game of two halves.

Controls
COD4 is a first-person run-and-gun game. You can sneak (and on some maps you have to) but for the most part it's shoot or be shot at. The controls are pretty good for this. Left stick moves you, right stick adjusts where you're looking. Various buttons crouch, jump, reload and fire. It's fairly intuitive to pick up and if you've played something like Drake's Fortune, the controls are sufficiently similar that it becomes a zero-learning-curve game. (Note - Drake's Fortune uses third-person camera - yuk. COD4 is first-person - ie. you look through your own eyes).

Graphics
The graphics in COD4 are good. Very good. Not brilliant, but a massive step up from the previous titles. The environments are detailed but the maps are relatively small. There is good texture mapping and use of colour and the global shadowing system is adequate. There are some problems though. There is a lot of aliasing on thin lines - power lines, cables - stuff like that. Aliasing is the stair-step effect (jaggies) that you get when a graphics system is unable to smooth out the differences in extreme contrast. For a console as power as a PS3, this shouldn't be a problem but it is. COD4 also suffers a lot of popup - where items pop in to view very late or change level of detail very late. This is particularly noticable on the Ambush map in multiplayer mode. The bricks and debris on the ground pops in in front of you almost in a wave as you run. Sandbags pop to their highest right in front of you and the burned out tanks in the middle of the map pop into high detail as you approach them. To start with you won't notice it, but once it catches your eye, you'll see it everywhere. Again - a PS3 shouldn't have this problem but COD4 is a multi-platform game so maybe they just coded to the lowest common denominator and didn't bother to tweak it for the PS3.
Smoke and particle effects are nice, but very processor-intensive. If someone pops a smoke grenade and you run through the smoke cloud, be prepared for very low framerates - it really bogs down. You'll see the same three or four textures used on smoke billowing through the smoke effects too so if you're waiting it out for the smoke to clear, you'll think "hey - deja vu - I just saw that exact same smoke."
There are specular highlights and bump maps used where you'd expect them to be used to pretty good effect. One of the neatest effects is the visual distortion you get around the muzzle of a gun during gunfire, or around an exploding grenade. Nice touch.
Occasionally you'll find faults in the graphics engine that make you wonder if the game didn't QA properly. On the Pipeline map for example, you can hop on to one of the oil tank rail cars and see through the oil tank. Sometimes when you die you'll fall out of the map or be able to see the inside of your character's head. The game runs at 60Hz for the most part, and in 720p it looks pretty good (but it's not full HD). There are places where it'll bring the PS3 to its knees though with the number of characters and effects all being drawn at once. Multiplayer mode on the Shipment and WetWork maps are good examples. You'll be lucky to ever see 60 frames per second on those maps.

Sound
The audio on COD4 is also pretty good. There's good stereo separation at the front and excellent use of the rear channels. Often you'll be able to hear someone behind you giving you more reaction time to do something about it. It's so seamless in COD4 that I've come to rely on it. The weapons effects are OK and they use the subwoofer to good effect. There's noticable differences in weapons types, with and without silencers, but I suppose only a gun nut would be able to tell you if they're right. There's a couple of mis-steps here too though - the Mini Uzi sounds like a child's toy for example. The voice talent is varied but too many of the English characters sound like Dick Van Dyke doing cockney. Come on - this is the 21st century - couldn't they get English people to do the English accents?

Single player
Single player mode is a good intro to COD4. The maps are varied and the missions are split between US and UK troops. Each mission is a mission-on-rails in that you really can't deviate much from what the developers want you to do. Go from A to B. Kill everything. Collect item. It's a tired formula but I guess it still works. As I said above, the maps are quite small and confined This is good because it means at no point during gameplay do you ever come across a loading screen unless you change maps or missions. It's bad because you can run from one side of the map to the other in about 30 seconds on the largest map which means there's not a lot of free-roaming capability. The game itself is mercifully short on cut-scenes so there isn't a lot of interruption. The cut scenes that do exist are a split between pre-rendered and game-engine scenes.
Without a doubt, the best single player mission is where you find yourself at the weapons controls of a C130 gunship. This entire level is played through an infrared sensor channel. You're orbiting a village and your task is to keep your troops on the ground safe from enemy attack. Your troops are marked with infrared beacons, so they all pulse or flash in the sensor view. You have three different guns at your disposal from rapid-fire machine gun to what-the-hell-was-that cannon. I think if you play COD4 through to the end, you'll eventually only ever re-play this level in single player mode.

Online
Online gameplay is where COD4 really shines in terms of fun factor. Unlike days of old where inexperienced players would drop into maps with 8 year old Korean kids who could snipe them through glitches in the map, COD4 has a load balancing system. As a newbie, you have zero experience points so you get put in games with other people way down the scale. This means you get a chance to learn the maps and figure out how best to play without the frustration of instantly dying because you re-spawned near someone who has a zillion hours of game time under their belt.
The more kills you get, the more matches you play, the more experience points you get. These unlock challenges and the ability to make your own weapons load (instead of choosing one of the predetermined ones) as well as perks. Perks are things like the ability to carry three grenades instead of one. As your experience increases, you get put in maps with other players with similar levels of experience. In this way it leads you into the all-guns-blazing experts-only matches quite gently.
There are a bunch of different online modes ranging from the usual capture the flags (Domination, straight from Halo), to headquarters, search-and-destroy and outright free-for-all and deathmatch. Team Tactical is a neat mode where each time only has three players, so the games become a lot more tactical. That mode also relies on headset chat otherwise you'll be running around completely uncoordinated. COD4 does support headsets chat, but until the first patch came out, there was no way to mute other players, which meant you were treated to levels of swearing that you probably had no idea existed in civilised society. Fortunately, now you can mute the players with Tourette's which makes it a lot more enjoyable. The problem is that a lot of people assume that because they've got an open mic and a captive audience, it gives them the right to behave like a total goon.

The biggest drawback of the online play is that the code isn't distributed. This means that one person's machine is hosting the game. If they get annoyed at losing a battle, or being shot too many times, they can cancel the entire match, resulting in a "host ended session" message for everyone else. This is really nasty. A lot of games use distributed online mode, meaning all the machines track the progress of the host in case it goes down. If it does, another player's machine becomes the host, seamlessly, and gameplay continues. GTA4 and Racedriver Grid both use this technique to great effect. For it to be missing from COD4 is criminal.
One thing that I'm still not quite used to in COD4 is bullet penetration. Get a sufficiently powerful weapon and a suitably thin wall and you can shoot other players through the wall. A lot of the time it's guesswork, but there are enough graphical glitches that you'll often be able to see another player's knees, elbows or backside poking through the back of a building when they think they're hiding. This is good if you're the attacker, but bad if you're the victim - you can often think you're suitably out-of-sight only to have someone fill your back with lead from the other side of the wall.

Three stars or four?
Very few games deserve 5-star rating at this point. The PS3 is still a relatively new platform and the developers are still learning how best to get everything they can out of it. Giving a game 5 stars implies the developers have nowhere left to turn for future improvements. This happens rarely.
COD4 is a three-star or four-star game but it's hard to choose which. In the end I went with four stars because of the fun factor. It's quick to pick up and the online play, despite the graphical and server glitches, has a high X-factor. It's hard to say what makes the game so much fun but it has that certain something that will probably keep you coming back. In the end, that's what it's all about. You can have all the hype and fanfare you like (are you listening Konami?), but if your game has spectacular graphics, a long and twisting storyline but no fun factor, people won't play it. COD4 has good graphics, good sound, mercifully little storyline and it's fun to play.