I would agree, for processors, I also prefer AMD, but when it comes to video cards, Nvidia all the way.
CUDA, Physx, 3d Vision. Just to name a few reasons....... Dont get me wrong, ATI has opencl, which can do some of what cuda can, but that doesnt compare to the speed of cuda. I do know, that Physx used to come as its own card, so technically, you can use that without an nvidia video card, and 3d vision is a new technology, that is released on the newer cards, that cost more then they are worth, for the average gamer.