For playing latest games i recommend using bootcamp instead of Parallels. The 3dmark06 benchmarks on my machine (early 2011 15'' Macbook pro, Radeon 6750M, using latest parallels and vmware fusion) speaks for themselves (rounded to fifties):
Code:
Version Mode Version Score Performance
Windows 7 Bootcamp Catalyst 11.11 9600 100%
Windows 7 Parallels Desktop 7.0.15052 7550 79%
Windows 7 VmWare Fusion 4.1.1 6550 68%
Windows XP Parallels Desktop 7.0.15052 5300 55%
Windows XP VmWare Fusion 4.1.1 5550 58%
All machines was set to 3GB ram and 2 cores. Graphics settings was on max.
NOTE: Windows XP cant use more than 256MB GPU RAM that is the reason why it scores so low.
NOTE2: Also, this table does not represent the performance on NVidia GPU's, on NVidia this may be completely different.