One of the things I'm always on the look out for is more great games on linux, I'm not THAT big of a fan of older arcade style gaming, I like to keep up with modern gaming like on windows, which I hate to admit, if you're a gamer it simply is the better option! But after heros of newerth came out I felt it showed that linux certainly is capable of having great games on it, one of those is 0 ad:

It is very similar to civilisation in game play and I loved that game, so naturally I love this game, it's only up to alpha 2 but you can get it here:

Very easy to install on ubuntu:
sudo add-apt-repository ppa:wfg/0ad
sudo apt-get update
sudo apt-get install 0ad
And after that it should appear in the 'games' menu. Have fun :D