One of the best, if not the best game I have ever played!
Good: This game has amazing graphics with realistic sounds too. Character models move in the game move very smoothly and they die realisticly (no rag-doll animations). Their mouths are in sync with the voices which give them a really realistic feel. The best part about COD4 is it's great story. I felt really hooked into everything in the game. The weapons are so realistic that sometimes one will feel wrong to inflict so much damage on a person. Also the AI in COD4 are very intelligent, THEY ACTUALLY HELP YOU IN COMBAT INSTEAD OF GETTING IN THE FREAKING WAY LIKE IN OTHER GAMES.
Bad: Some minor graphical glitches in the game. The main flaw about COD4 is that the story is really short, about half the average of modern day shooters. It will probably take you 4-6 hours to beat, but the guys at Infinity Ward (creators of COD4) really made it up by making the story very realistic and great. When it ends, one will get a sense of accomplishment but also sadness because there unlike other shooters where after beating the game, that the world becomes a better place, COD4 makes it so that after the war has ended, the world feels like a hell-hole. Another perk of COD4 is that it has an awesome multi-player and plenty to unlock in it, about 10+ more extra hours of game play.