I've played COD2 through 2 times, and I've played quite a bit of multiplayer. There really isn't much re-play value in sp even at harder levels. One MAJOR problem with the mp is they didn't include cheat protection. Nothing worse than hit someone with 2 grenades and shoot them only to have them turn around and frag you.
IW is promising some version of punk buster early this year, but we'll wait and see. Also, mp has very limited maps, and IW didn't include a map-makers. Seems to the COD community that IW has little interest in supporting their customers to keep the game going (as with UT2004, et. al.)
The graphics are great, but once you've beaten it a couple of times loses the interest.
MHO...... Lt. Dan