Now, let me just clear some things. I'm a HUGE Halo, 2 and 3 fan, and they have great (yet disappointing) campaigns. I've played Battlefield (Vietnam, 2, you name it I've tried it). They all have great graphics. They are all great.
However, last night I slept over at a friend's house and found he had recently purchased Call of Duty 4. I had brought my 360 and he has a MASSIVE High Def TV. But before I played, we watched him play. The whole campaign.
The campaign is the most heart pounding and intense campaign ever. Infinity Ward paid attention to detail. Literally every act has a "holy !@#$%" moment. The graphics, sound, weapon balance, just... EVERYTHING is amazing. The characters are believable as well.
Then after watching him play for 8 hours straight, we 4 way'd multiplayer. We played that for another 8 hours. It was like... Halo's fun mixed with competition. Just a note because I can: I won every single game, team or not =D.
After about 20 hours after first seeing the start screen, I stopped and took a breathe. I said "10 out of 10 material" and everyone agreed. CoD4 is the ONLY game to ever have me play and love it so much.
Just a note, I have played and finished all Call of Dutys (only 2 on Veteran... which took forever).
Hell yes to CoD4. I'm off to play the campaign on Veteran.