any card should run 2d games fine. what game do you plan to run?
as for numbers all over the palce, that is to be expected. Most ATI cards are optomised for max Direct X 9 performance and Nvidia Cards tend to do better in OpenGL game performance. DOOM3 runs like carp on radeons but Nvidia runs it well, likewise, Half Life 2 has a advantage for ATI(fx5xxx series cant even run it in Direct X 9 format without it being unplayable at decent resolutions, the 6 series fixed this but it still lags behind the radeons somewhat.)
Also, remember the GeForce4 Tis run Direct X 8 so it wil;l be faster at equalivent settings than a card running Direct X 9 since Direct X 8 has lower image quality.