CoD4 is a great game, great multi-player. A game you can't play for just an hour, very addictive!
The graphics are amazing! The on-line community is great, with the exception of a few bad apples. The weapon selection is good. The playing maps are great (especially the add-ons) with just enough hiding places for great "sneak-ability". My recommendation is to play the single player mode first to get more acclimated to your weapons and on mastering the art of slicing your opponent's throat. =) If you like playing as a sniper, this game is right on! It is very close to the real thing! (You have to hold your breath to shoot accurately!!) Great game for beginners because even though you're learning, the game it is fun and the on-line community is great for pointers. Definitely the best CoD so far.