Look realistically if you want to be playing 'current releases' game wise then you simply DO NOT want to be doing it in a virtual environment.
Games are probably the most resource hungry things on PC's these days and require every single last grunt of power to make the most of them.
As good as all the virtual solutions are... the simple truth is they are designed for general applications and not gaming. Sure they have made efforts to include DX 8.1 - but hell how long has DX9 been the defacto for gaming (5,6 years ?) so you are still at the end of the day crippled.
There are solutions to the problem.
Install windows in bootcamp. Install the game and enjoy all the fun of the fair with your mac being used to it's advantage.
You can still use parallels with your BC partition inside Mac OSX if you need to quick boot up the PC side of things for other day to day tasks.
That way you only have one version of XP / Vista installed, and the choice of using it in a virtual or native environment.