Ubuntu 13.04 Desktop Gaming Performance Comparison
The OpenArena 0.8.8 results aren't really surprising now: the lightweight desktop environments led to the best performance, although it's a bit surprising Enlightenment wasn't running any faster.
Ditto.
There was little difference in the Prey id Tech 4 results aside from Unity running slower than the rest. Using the KDE Plasma 4.10 pre-release also led to a dip in the frame-rate.