Yes and no, I've been playing on hardcore difficulty as they tend to be quite easy (CoD3 was not very good - it was so easy), but the single player game is basically just a free add on for the multiplayer game. The online multiplayer is brilliant, especially the team deathmatches and if you have the
PC version (or even the 360 version) I would highly recommend you try it out. Since CoD2, the series has mostly been a multiplayer game with the single player mode just there to give you some bonus content
IMHO. CoD3 was a different developer which is why their multiplayer was awful (and it was console only which didnt help). CoD4 (on
PC) is some of the best multiplayer I have every played and will probably add up to cause the next dakka release to go back by a month