I know what you're thinking, expansion packs aren't as good as the original. Well you're wrong this time.

User Rating: 10 | Warhammer 40,000: Dawn of War - Dark Crusade PC
First off, this is an expansion pack. Of course, you should already know that if you read my little description. It's a stand alone expansion as well, so you can play it without the original game. But without the original or the first expansion, you can only use the 2 races introduced in this expansion while in mulitiplay. In singleplay you can use them all.
The campaign is non linear, and you choose where to attack next. It takes place on a Risk-esque map. You can play as any of the 7 races in the campaign. The 2 new races are the Tau and Necron. Both of which are really good.

Bottom line, BUY THIS GAME. Even if you don't have the original. This is much better than the original.