I haven't seen many games that require the latest and greatest computer equipment.
Even Half-Life 2 only requires a DirectX 7 video card to actually play the game. You won't get the beautiful shaders or anything, but you can still play it.
Having said that, the majority of people that do own the latest and greatest computers still use a Microsoft Windows OS, so it's still part of the largest marketshare.
Also, towards Mkreku, if DirectX was the only thing that made games OS dependent, then I'm pretty sure that a game like Neverwinter Nights would probably have made it to Linux as well (Neverwinter Nights engine is OpenGL).
Also, just from experience this past year, the difference in compilers alone makes "recompiling" code more difficult. The work I did this summer utilized only open source libraries on Linux, and we repeatedly broke the Windows build when making minor tweaks to the code. Eventually it got so broken we just said Fark It and continued with the Linux build exclusively.