Mmmmm, i offer some cliched comments :
1) A camera is a tool
2) Different brand/make of lenses offer different optical signature
3) The Leica attained celebrity status partly due to Magnum, and
their famous users: HCB, Robert Capa...
4) In a low-light, unobtrusive environment, there are very few competitors
mainly because (related to the Leica M mystique):
a. Leica is 35mm format and in that era (in the 1940-1970?),
cameras are much bigger and more intimidating.
Even a current SLR with flash is still bulkier/more visible than Leica M.
Admittedly, Minox and the current crop of slim digi-cam is so much
smaller than their 35mm brethen, the quality is not there yet (refer to b).
b. Leica M has very little shutter lag and better handholdability.
(Of course, this applies to other well-built rangefinders,
e.g. Hexar, Contax G)
c. Leica M has another strength in that its lens performed very well in
wide open aperture.
Using high ASA film (or B&W), big aperture and low shutter speed,
Leica M can capture intimate indoor picture with little disturbance
that very few cameras can.
d. Leica M is mechanical and was designed/made in Germany (then).
It is now manufactured in Canada.
But time has moved on, and people are less attached to mechanical workings.
E.g.1 a watch may cost $10k for its watch movement but
a $20 casio can tell time as well/ or even more accurately
than the immaculately machined, intricate gear, wheel, pinion, winding blah,
blah, blah....
E.g.2 A cheapo Kodak disposable camera can render a more realistic picture
than Cezanne's apple or Monet's morning on the Seine, but technology
advance cannot discount anything from the works of the masters
All in all, Leica M is a niche market, excels in a particularly narrow segment:
Low light hand held photography (no-flash and preferably B&W)
If you make a living in an aperture lower than F2.8, no flash, B&W,
paparazzi environment, who enjoys 8R or greater blowup, no zoom,
prefered wide angle to long focal length (preferably max at 100mm)
Leica M has very few competitors.
But I admit that owning a Leica does not immediately make you a photographer. Similarly, not owning a Leica does not degrade
you to a non-photographer.