Phoronix has recently conducted a total of 165 graphics tests on six different hardware configurations comparing Windows 7 and Ubuntu 10.04 using their flagship Phoronix test suite. That level of benchmarking is enough to give us some impressive amount of data.
They ran games from various engines and tested their performance on all these configurations. The results were astounding. Quoting them,
The Intel Linux graphics driver is the real loser in these tests where it is easily and always clobbered by the Intel Windows. While the Intel Linux graphics driver is open-source and has made great strides over the past quarters with kernel mode-setting, a new 2D acceleration architecture (UXA), in-kernel memory management (GEM), a migration to DRI2, and other improvements, its performance is a joke.
It is unlikely we will see Intel’s Linux graphics driver recoup any of these major performance losses anytime soon as they are not even committed to switching to the Gallium3D architecture that is faster than the classic Mesa DRI drivers.
Ubuntu recorded a win with the NVIDIA GeForce 9800GTX where it beats Windows 7 by a significant margin.
This clearly shows that, even though there has been development relative to what Ubuntu Graphics has been in the past, it is not developing as fast as graphics on Windows.