Microsoft continues to add to its “Games on Demand” digital download service today with the addition of the award winning underwater FPS BioShock and the epic strategy game Sid Meier’s Civilization Revolution.

Both titles will set you back $29.99 and about 5GB of hard drive space, but if you’re sporting a brand new $299 120GB Elite Xbox 360 model, you’ll have no problem fitting them.

With the addition of these two titles, the “Games on Demand” section has some exciting titles among its ranks including Assassin’s Creed, LEGO Star Wars: TCS, Kameo, Battlefield: Bad Company, Mass Effect, Burnout Paradise, The Elder Scrolls: Oblivion, Need For Speed Pro Street and Carbon, and many more.

BioShock, Civilization Revolution added to Games on Demand

The full-on digital revolution is undoubtedly upon us. Anyone caved yet? Or do you still support brick and mortar retail outlets like Best Buy, GameStop and the like?