I dont know about your selections, but i do know that there is a reason why they use the games they do and its because they represent a broad range of hardware requirement situations.
To explain further, some games need more in the way of textures, some need shaders. Others like Microsoft Flight Simulator are more CPU centred and are there to show that side of the coin. ATI cards will do better with som egames and vive versa.
Im sure that when some games that meet the needs of the tests and are more suited/ relevant to todays gaming comunity that toms will update them.
As far as XP only goes, well i have recently built a new rig and i installed XP again. I do think that all reviews should include both Vista and XP though. I realy think we are close to the point where there is no longer any serious FPS/performance reasons from a gaming point of view to shun Vista for that much longer.
If i was building today or even last month i probably would have gone with Vista but unfortunatly you have to draw the line somewhere. I did however build with the idea that it will be upgraded to Vista at some point, I dont think i will need a new motherboard for a few years (unless Nehalem is so stagering and games come out that cant cope with an extreme core 2 that is), and Motherboard aside i have plenty of upgrade options.
Ok well you should get high settings on most things but Ultra i honestly dont know. Your system dosent lok to have any weak points given the res you are stating. The only thing i would look at upgrading if you are looking for more performance is swapping the 8800GT for a 4850.