I wouldn’t discount AMD just yet. They closed quite a big gap in the server cpu market against Intel, most probably due to better leadership and management. I wouldn’t be surprised if they are able to pull that trick a second time with GPUs. 2 years isn’t short but it isn’t that long either.

People have said AAPL was overvalued perennially as long as I remember yet their market performance seems to ignore these opinions.

On the other hand, a big part of it also comes down to the tool chain, and NVIDIA owns CUDA. Until OpenCL or other gpu platforms catch up, it seems like NVIDIA can continue to corner the gpu market at large.