I tried both. Contax G2 and Leica M7.
The Contax is OK, specially the Zeiss lenses but you can not compare with a Leica M7. The M7 is more than OK and so I decided to fill in my budget for Eur. 3300,00 with a M7, Elmarit 2,8/28mm and a Summicron 2,0/50mm. A lot of money for such a camera but I had luck to get it, even (almost) new. (Mostly a matter of time).
If you're working professional with this camera and put a real good film inside e.g. Fuji Acros 100 or Rollei PAN25 or a high resolution Copex with Nanospeed developer you can go till 40X50 cm enlargements and have shootings on low light level conditions and rather low shutter speeds (1/15 S).
I am very satisfied with this working tool. Everything is working simple but I personaly like the AE-mode very much. Also the automatic DX is working fine. Manual of course possible. I do not understand critics on those points.
The only thing which needs some adaptation of the photographer is film change. Not quick but due to the flatness for film, Leica still have the old system of filmloading.
I can only recommend a Leica M as rangefinder camera. But of course I am aware of the investment for such a camera.