The reason I stick with Nvidia is because you're basically a beta tester by buying Intel or AMD GPU that simply lack the features Nvidia software has.
Yesterday I was talking to someone who had screen tearing in their game, and I said I just set the game at the desired framerate through Nvidia's control panel. He uses an AMD GPU and his reaction was one of disbelief, the fact I could just lock the framerate per application, even my browser's FPS.
He is now considering an Nvidia GPU.
To compete with Nvidia, it will require a lot better software and drivers than the garbage AMD and Intel are putting out.
Neither AMD or Intel even has native DX9 support, they're not even beta products, they're just missing core features. It's an afterthought for AMD and Intel. With Nvidia, GPU is their core business, and it shows.
People said Intel selling dedicated GPU would be good for the consumer. No it's not, it has been nothing but issues, Intel is releasing half-assed drivers just like AMD.
I consider the only real competition to Nvidia being ARM with PowerVR, Qualcomm, general Mali (ST micro / Samsung etc).