A web based Linux game store has been launched very recently and is christened Gameolith.
The service is meant to offer a simple and more convenient method for Ubuntu and other such Linux based OS users to download their favourite Linux games that are available commercially that come with bundled DRM. The games have packages and tar balls for Debian, Ubuntu and fedora Linux distributions.
http://ubuntumanual.org/posts/373/online-game-store-launched-for-linux-community
http://www.gameolith.com/
I'm not sure I see the worth of this, Ubuntu already has the Software Centre. The only distros that seem to benefit from this is *buntu derivatives that do not use the Ubuntu Software Centre.