MDK2 is a rather simple OpenGL game by today's standards. It does not support fancy 3D features, and this is exactly what makes it interesting for benchmarking. Then again, a difference of 4 fps does not really make a huge difference.
The scene is similar at 1600x1200: all cards are equally suitable for this resolution, running MDK2 on our Athlon 1200 system at > 80 fps. It's nice to see how the GeForce2 cards are being outperformed. The GTS in particular suffers from its low memory bandwidth.