The configuration don't work properly on Windows 8, theres no resolution to set you are forced to play on lowest resolution, even with my GTX460 the game looks crap in this lower resolution.
So the problem is:
-> Theres no option in the dropdown menu of resolution is all blank.
->No option in the rate menu either.

Tip, if your using Windows 8, dont buy it.

Same problem here....methinks GOG was a bit too quick marking this game Windows 8 compatible

Same problem with the resolution. I am getting an error message stating that my drivers are not up to date (latest NVidia 310.06 for Win8).

However, I am able to change the settings for Anti-Alias and other advanced graphic settings. Resolution is not great for my 23in monitor, but at least the details are on par with what I remember from the game.

I was able to change the resolution by going to the "Beyond Good & Evil Settings" executable and changing the compatibility to "Windows XP Service Pack 3". See if that works.

Did you try changing the Resolution "by hand"?
there is a d3d9.ini in the game folder, where you can change the resolution.

I do not have a win8 PC, so I cannot test it myself,
hope this helps