Hi Charlie,
these are 2 totally different worlds. Both in use and in image quality. You need to tell us more what you are planning to shoot.
The relatively new lens design of the G-system is significant better in image quality than the old Nikon F lenses.
But also in use, a Nikon F4 is a beast, big and heavy compared to the Contax G2. Personally I would always choose a Contax G2 system over an old Nikon F4 system, but this has also to do with what I am shooting and how I do plan to use it.
The Contax G2 is similar to a Fuji XPro. It is small, light, and you can take it easily with yout without always beeing noticed. The viewfinder on the left side makes a big difference while shooting. You can interact better with people.
The G lenses 21/28/35/45/90 are tiny and light and have all excellent image quality. They will shine with b&w.
But there are no option for tele-lenses longer than 90mm and the G2 system is neither made for sports.
Will you shoot people? landscape? sport?
What do you have already as an equipment and what is your expercience with it?
