Browse to the Gothic II / system folder and open the Gothic.ini file. Scroll down to
enableJoystick=0
and change it to
enableJoystick=1
then you can re-map the controls in the menu.
I also recommend that you change both
zVidEnableAntiAliasing=0
zTexAnisotropicFiltering=0
to
zVidEnableAntiAliasing=1
zTexAnisotropicFiltering=1
Most modern PCs will have no problem with these settings and it improves the graphics a lot.
There are many other settings you can change here but I imagine you should do so with caution.
Maybe someone else has other knowledge on how to improve visuals and/or performance?
I have a PS2 to USB adaptor that allows me to use a PS2 controller on my PC. Let me tell you that Gothic 2 works beautifully using a controller and I can't imagine playing it another way. The new XBox 360 controllers would probably be great too. That's my next purchase so I don't have to use an adaptor