Currently, AMD cards are off-chart for linux gamers, as even OSS drivers are working better and faster than proprietary ones. But OSS drivers are lacking (yet) some major features and modern OpenGL support, so many games are just not supported yet. Plus, many of newly incorporated features like float textures or S3TC support require git kernel, recompiled mesa (with enable patented) or some bindist-unavailable software (libtxc_dxtn), which makes OSS drivers badly available for many of binary-distributions users.
Just few hot-topic examples:
1) Starcraft 2: on NVidia working perfectly and after drivers update FPS are even better then on Windows. Fglrx suffering from multiply graphics bugs and require some extensive magic to be even playable. FPS are far from Windows ones. OSS not tested.
2) Bulletstorm: on NVidia working, but FPS are low. Playable, but without saving (no GfW). On fglrx it's starting only from 11.4 driver version and suffers from terrible graphics miscolor. FPS are terrible. OSS drivers are working mostly ok (on 39_rc* kernel and git mesa with --enable-patented and libtxc_dxtn), but with some black bounding-boxes bug. FPS are better than of fglrx, it would be even playable if not black-bounding-boxes.
3) Portal 2: on NVidia working perfectly and with good FPS. On fglrx it's runnable only with 11.4 driver version (which was released few weeks after P2 release), but suffers from multiply crashes on high settings and low FPS.
4) Dead Space 1/2 (same engine): On NVidia working mostly perfectly and with good FPS. On fglrx it crashes in many cases, suffers from multiply graphics bugs, missing effects and so on.
And such situation is for many games: nvidia - ok, fglrx - fail, oss - not yet ready. Therefore - most of wine games are on NVidia. And as heavy discrete graphics systems like HD5/6 are required mostly for games (or some professional software, unavailable on Linux too) - this means lost hi-end market for AMD. And this situation could not be changed by just somehow suddenly releasing ideal drivers - AMD's reputation is already bad and many people don't believe that OSS drivers may change it (mostly because they don't see their's fast progression due to bindists' inertia). AMD should do something really new and progressive, which was never made by NVidia, if they want this market. DX API support is just that thing. But, imo, AMD just don't want this market =).
Originally posted by Djhg2000
But Linux... Well, it would be loss of money, by now, IMO.