Pretty much anything set in the Warhammer: 40,000 universe other than what we have now. The Dawn of War series has been out for a while, and I honestly haven't played Space Hulk, and Space Marine is aging. Other than that, a lot of the recent releases with 40K have been pretty...meh. 

Warhammer 40K is a great universe for pretty much any genre: strategy, action, RPG, hell, even a more adventure-oriented game (ala Telltale Games) could get pulled off. It's a versatile universe for gaming. Think the concept I'd like to see be done with it would pretty much be Dragon Age: Warhammer 40K. That'd make me cry tears of joy. That, or a Total War: Warhammer 40K.