You may have to google some of these, but as far as nice looking, polished games go:
Battle for Wesnoth
Pingus
Neverball
I have no tomatoes
Frets on Fire
Legends the game
Open Arena
Warsow
Urban Terror
Funky Funguloids
Mania Drive
Super Tux
Secret Mario Chronicles
Chromium
FloboPuyo
Torcs
Dark Oberon
Globulation
Wormux
VDrift
These are all very good looking games, and ought to keep you busy for a while
At the moment, my favorites- Legends, Urban Terror and wesnoth
Bookmarks