There are lots of market surveys for video cards, e.g.:
http://www.xbitlabs.com/news/video/display/20071029062106...http://xtreview.com/addcomment-id-1771-view-ATi-vs-Nvidia...
The basic bottom line is that NVIDIA, Intel, and ATI are popular,
but it's hard to say NVIDIA dominates the WHOLE market.
NVIDIA is popular at the high end, Intel is popular on Intel chips
(esp. laptops), and ATI is popular on AMD chips.
I don't buy the argument that the large number of crashes is
due primarily to NVIDIA's popularity. There are LOTS of complex devices
in a modern computer. Fundamentally, if a particular driver is one
of the primary causes of an OS crashing, then the driver is bad.
By definition!