Some great ideas for part 2, thanks a lot!
One of the first DX10 games released was Call of Juarez. It was virtually unplayable in DX10 mode with all the options turned on. Of course, Crysis got all the attention but Crysis came like 1 year later. Call of Juarez really made DX10 look bad compared to DX9 (due to horrible performance) that it made many of us just hold off on upgrading.
Quake1 was probably the biggest video card "killer app" of all time..., only to be intensified with Quake2 (with its native OpenGL support).
How can we not mention Doom? And Wolfenstein 3D?!? Doom 1 was the reason that many people did a complete overhaul of their mobo's/CPU's, in order to turn it from a slide-show to a fluid experience. Basically, Doom is what started it all. Then we were able to play Sim City 2000, etc.. all thanks to Doom.. LOL!
Given the huge popularity of Half Life and its Counter Strike, everybody were quickly ditching their computers from the K6/Pentium1 era to the Pentium3/Athlon era. Right around the year 2000 was the probably the biggest and most rapid change in the computer hardware requirements. Most games started requiring 64MB instead of 8MB memory--an 8x increase within 1 year! Now, we're not seeing anything that rapid in computer tech... not even Crysis is increasing the memory requirements any more than 2x than what a 2+ year old game needed.