CoD 4 has a compelling story, and awesome multi player.
Then a friend one day forced me to take it and play it. And i loved it. The story is fast paced and action packed. It has you take two sides the USMC and SAS. Infinity Ward or Activision (which ever made the game) finally took a more realistic view on how the Marines and other military forces around the world actually work. They no longer make them out to be the worlds biggest bad a$$'s that always are pumped full of adrenaline. The dev's use actual terminology from the marines and other military forces which gives it a more authentic feel to it. But enough about that
The actual story takes place in modern times with a middle-eastern country and Russia teamed up to take down the world with nuclear weapons. You progress through the story switching between the views of two characters "Soap MacTarvish" of the SAS and "Sgt. Johnson" of the USMC. Although you play more of the SAS then the USMC. The story is very simple from a far its basically this "Try and find who has the nuclear bomb". But if you get into the story its more complex and emotional as you get attached to the characters. Which makes the end leave you with a feeling of satisfaction because you just saved the world.
The multi-player is just amazing. Even though achievement whores might not stay for long because theres "no achievements whats the point" remember the time when you played games for fun not for achievements?!
The exp. system they have set up is fun and (for you not achievement whores) will make want to say. You can customize everything you fight with from guns to grenades and you can even get perks to do special things like sprint for longer, etc... If you love multi-player kill everything in site games this is perfect for you
But alas every game has there faults. The dialog is kind of cheesy along with the voice acting. The difficulty is insanely hard at harden and veteran to point where if your enemy runs up to you and he has a machine gun (WHICH HE WILL!) and get the first shot its almost impossible to to get you gun down because for some reason when you get shot the world turns white and red and your gun proceeds to aim higher with every shot this gets aggravating after the first 10 times that it WILL happen. I don't know if the dev's want to have a realistic game but it comes to a point where reality in games goes to far.
And if it was reality they were shooting for they missed it in some points by a long shot. I'd be standing and the middle of a gun fight and all the bad guys would shoot at me, ME not my allies standing 3 paces to the right but me and only me! Its like my allies paid them off during the loading screen too kill me. Along with the enemies sole targeting and hatred for me they seem to be able to spot you be hind walls.
The health system seems to be the same as most modern first person shooters. You get hit the screen turns red and you run away to twiddle your thumbs in the corner until your character decides that he is okay. This has its ups and down because the AI have no desire to live for long because they will run halfway across the field to come up beside you when you are twiddling your thumbs and kill you.
All in all CoD 4 is a great game that anybody should own and probably will enjoy