It's like simultaneous Chess with guns. Also, shotguns ftw.

This three-player survival game is awesome. It's incredibly difficult (took me well over 100 hours before I managed to beat it) and has literally thousands of different strategies. Every time you level up, you get access to a new piece of wargear (up to 20 levels), and there two unlockable gear for every race. For $10 (or less on sale), it is well worth the price, and this game is being updated over time with new content.

Dawn of War 2 is not your typical RTS game. You have only your starting HQ, which builds all of your units. You also start out with one of three commanders, depending on which race you pick. All upgrades are done from the unit squads themselves.
This allows for immediate action from the get go and the battle is never decided in one battle. In almost all of my games, I have at least three full army vs. full army conflicts, and it's typically a back and forth type thing. This game is built around strategy of the units and micro management of them and their abilities.

If by chance you don't like the multiplayer, there's always Last Stand mode, where you and two others defend against waves of enemies with your hero units that constantly gain upgrades as you level up. I've never beaten it, as it is extremely challenging. Also, it has the most amazing campaign I've ever played. Not to mention co-op.

DoW2 Gold Edition is well worth it for its price, and it's a bargain when it goes half off.