Playdeb is a gaming repository for Ubuntu – aimed to provide titles already available on in an easier to install and update format.You can get great deal of ubuntu games just with PlayDeb installed.
Install PlayDeb

Download here and double click to install.

Or configure the repository manually:

Go to System-Administration-Software Sources, Third-Party Software tab, Add:

deb jaunty-getdeb games

Add the repository GPG key, open a terminal window and type:

 wget -O- | sudo apt-key add -

Now,go to this page ,choose the game you want to install and click the “Install this now” button below the screenshot of the desired game.