I received Call of Duty for PS2 for Christmas 2004. It's taken me a couple of months of sporadic play to complete it. I'm not particularly inept at games, but I found this one quite hard! The levels were vast, with the VERY occasional "checkpoint" mid-way through. If you die, you're taken back to the start, or to the checkpoint if applicable. Some levels took me over 30 minutes to complete, so you can imagine the frustration if you're taken back to the start!
This game's strengths are it's graphics, it's atmosphere, and the sense of actually being there. It surpasses Frontline in this respect to me. The places are beautifully rendered, and the weather and sound are great.
The enemies are intelligent, and you do have to play sensibly to progress with reasonable health. By sensibly I mean allow your colleagues to get THEIR arses shot to ribbons whilst you hide in an alley way, then lob a few grenades out. You also have to be sensible with your ammo. You can only carry 2 weapons, which actually means you need to think strategically about which ones to carry, and to be conservative with your shooting.
The graphics too are fantastic, and as another reviewer has commented, the number of soldiers on screen at any one time is impressive. Wasn't so impressed with the tank missions though. They went on a bit long and I was dying (not literally) to get back out on foot and "make mayhem" with the boys!
Although it took me 2 months to complete, had I played every night solidly I suspect I would have finished in a week. It was a bit on the short side in hindsight, but it's the sort of game I'll want to play again in the future, and it'll all seem new again. Highly recommended, intelligent first-person shooter.