Warhammer 40,000: Dawn of War II: Retribution
Let it never be said that Relic, the developers behind Dawn of War II, doesn't understand the concept of an expansion pack. With Chaos Rising they upped the stakes, of both the storyline and the gameplay by introducing new gameplay elements, the story getting grander and introducing another faction...
Ability to play as six diverse races; combat is intense and action packed as ever; the Imperial Guard is quite a game changer in multiplayer; new Last Stand arena is hard as hell
Levels are reused in their entirety in single player campaign; campaign missions grow repetitive; slightly muddled narrative from first two games