Virtualising the video card is gonna be problematic, because it's not exactly a priority/purpose of such apps, as far as I know. VirtualBox, for example, can't even have more than 256MB memory dedicated to video, even with 3D acceleration enabled, and its Direct3D support (even for as much as Aero) is still experimental. You can install DirectX - the software, but you'll still be left with a generic VirtualBox Display Adapter, which won't be good for gaming. Meaning the CPU is gonna have to handle all the load, in a whole system that is operating entirely above the one handling your physical machine. Not saying it's impossible (from a hardware pov; DX support and operation is an entirely different matter), but you'll be needing a rather extremely overpowered rig to have a chance at complex 3D gaming in a virtualised environment. Especially if you don't want it to be a slideshow.