All these games and hopefully much more will be available for Ubuntu users, via Ubuntu Software Center, as soon as they are finished and the Unity 4.0 engine is out.
Unity 4.0 is developed these days by Unity Technologies, which are getting ready to release the final version of the award-winning game engine, and a collaboration with Canonical will make sure that game developers can publish their games directly into Ubuntu.
And to be honest, I just can't wait for both Unity 4 and Valve's Steam to break the ice, to destroy that giant door that keeps Linux users away from all those nice games we see on our neighbor's computer!