COD 4 is intense. Its heavily scripted, no open solution. You go where you suppose, shot at the enemy and move on. But, COD4 is one of the few games i will replay. The single player experience is very rewarding. Like beeing in Ridley Scotts movie "Black Hawk Down..."
Being short on time, i am one of them who think shorter game is good. SP campagin can be played through within 5-7 hours... what i have read. Escpecially short FPS games help me not loose my interest.
The missions in COD4 is very impressive. The landfall (from sea) with a massive armada with helicopters, Its just "right". I have no clue how the multiplayer aspects are in cod 4, but i will soon find out. Hopefully on a private server. One mention against COD 4 multiplayer is "small" maps. Don't know if thats right.
COD4 is like a interactive movie. Good looking, intense action, and ju just want to see what happends next.
But, like i said. If scripted actions isn't your cup of tea move elsewhere. I realy really like the move to modern warfare!!
Oh - you asked if it was good.
Back to Crysis...which is more open in design and will probably let other people enjoy it better. Its not depended on scripting as heavily as COD4.
On my medioker machine (AMD X2 4000, 2GB ram, 7800GTX) COD4 is a beautiful looker. Crysis withits poppin texture is annoying. A better computer and the graphics in crysis is probably better...