My pick is simple. Warhammer 40,000: Dawn of War - Dark Crusade. Nothing else released this year has attracted the same amount of attention from me as that. The single player campaign is awesome. The multiplayer is awesome. The two new races are awesome. If you don't have the original 2 games, you still get to play the two new races (in multiplayer, you still get all in single player, I think), which is plenty.
I really don't have much to say besides that it's an awesome real-time strategy game, regardless of whether or not it's based on a real-life tabletop game. The unit quotes are excellent - entertaining at worst. The campaign is simple, yet quite fun. All you have to do is conquer a limited set of regions. All of them give you some kind of bonus - be it when you begin a mission, or which missions you get to pick from. After eliminating the other six races also on Kronus - you win.
The skirmish mode is excellent with the AI able to give you some sort of challenge. The only gripe people might have is the relatively low cap on squads and vehicles which really limits the amount of crazy things you can do. The game compensates by having each race have one relic unit (which is a really powerful unit or vehicle) to help with the game. :D
"I command the dark powers." - Chaos Sorceror, Warhammer 40000: Dawn of War
(I have updated to another version of Wordpress, 2.1, so watch out for the bugs, and report any if you find them, if not for me, For the Dark Gods. :D )