Company of Heroes, a few years old, but a very fun game.
Men of War is a much more realistic but WAY harder game to play...
it uses an inventory system and stuff, so you're soldiers can run out of bullets if you are not prepared or havent looted dead bodies. And its not the typical build a base and build soldiers and armor (which is what company of heroes does)... in most of the game, they give you a set number of people and you are allowed to send reinforcements but the game mostly focuses on the fight.
You don't need any serious hardware to run it and the AI is not half bad.
My favorite part of the game was getting my flamethrower soldiers to heat up a enemy tank. Then the enemy tank drivers get out of the tank, you gun them down and then you can take the tank after it cools down..pretty good stuff right there.