You're looking for emulation, not virtualization. You'll have more luck if you search for it that way. You can essentially think of the difference as emulation creates a new layer that emulates a piece of hardware for an OS to use. Virtualization splits up and manages the usage of a physical device that is already there. Some virtualization software also does emulation of various pieces of hardware. For instance, both VMWware Workstation and VirtualBox will give you the choice of various hard drive controllers and sound cards. I think qemu and bochs can even emulate different CPU architectures that you don't have, which is cool. But you'll have to check on that. I'm not sure about software that will emulate a graphics card, haven't seen that in any of the apps I've used. I think it would be a lot slower than you might expect it to be if you're wanting to do 3d acceleration or something.
What are you trying to accomplish by emulating a different graphics card?