Call of Duty 4 is one of the best looking, and most intense games so far this generation.
Not much needs to be said about this title, Its amazing, and you can't say that many different times. The one bad thing about the game is the story's length, it's pretty short. But COD4 does a great job of immersing you into the story and if you sit down and play it for a while, you completely forget about your surroundings and the hours fly by.
Like all Call of Duty games, the fights are INTENSE. And in Call of Duty 4, they are quite possibly the most intense they've ever been. With tons of enemies surrounding you, you are constantly struggling to get to a new area of cover where you aren't exposed. The fights are very fast paced and there are lots of them. Though short, this is the best single player CoD yet.
Multiplayer is AMAZING. Near every game I've played I've heard "Halo 3 sucks, I'm never going back to again" or some other variation of that statement, and quite honestly I'm starting to believe it. It is just a lot funner than the same Halo you've been playing for years. There are even a little bit of RPG elements in there. Every kill you get gives you XP and with more and more XP you will unlock new weapons, new camo, new skills, and the ability to create your own class. You'll probably never find someone equipped the exact same way you are in any game.
Over all, Call of Duty 4 is amazing. It's about time that WWII was left behind, and the intense modern warfare was adapted. Hopefully Treyarch won't screw up a good thing on Call of Duty 5