One of the problems with 3D games is the fact some game developers only support the Tegra 2 chipset, the GPU in the Mediapad is based on the Qualcomm/Snapdragon chipset with a Adreno 220 GPU instead (technically many say this chipset with the Adreno 220 GPU is more advanced, as it was released after the Tegra 2 chipset but as the Tegra got more of a foothold in the tablet market, it has been hard for the Adreno to get the same support in tablet games, there seems to be allot more phone handsets that use the Adreno chipset compared to tablets).
The app store checks what your devices configuration is and only shows games that use the chipset your device supports.However all games use the same graphics API (OpenGL ES) so there is a workaround called 'Chainfire 3D'. This program sits between OpenGL and the program and makes the mediapad look like it has a Tegra chipset and patches the calls to OpenGL.
The free version of the app does let you run games this way but does not patch the app store so you cannot list the games so this means you need to buy the full version (its a couple of £'s but not much and worth it if you can get a game you like to work).
Of course as more tablets are released with the Adreno 220 then more game publishers will directly support it, Technically there is no reason for the 220 to not run all Tegra 2 games.