Possibly the best RTS game ever created
The story line for World In Conflict is basically a third world war, between Russia and the USA, an interesting and highly plausible occurrence. The game play during the campaign is simply marvelous, with inspiring cut scenes, and some pretty interesting missions that you have to achieve in every scenario.
I highly recommend that you buy this game, even if you aren't that interested in RTS games, the intense action in this game will get you hooked on to it immediately.