I turned from wide (28) to standard (50) in the past years. When I began shooting with a M6, 28mm was my most used focal length, especially when used outdoors. Later, a 35mm lens became my standard. Then, the 40mm Nokton was released and mine didn't leave the camera much for more than a year. Then I rediscovered my 50 Summicron (collapsible), as I found after all I had to crop too much from most of my 40mm shots. Since I use a R-D1, the 35mm (aka 52mm field of view) lenses get most usage again. Actually, the Color Skopar 35/2.5 (P-I) fits my needs best in terms of focal length and compactness (which let me accept the relative slowness of f2.5 better).
There is no perfect standard lens, especially when you rarely leave the house with more than one, but I find with the 50mm field of view I have the highest "no cropping needed" rate. As for other focal lengths, my legs are my zoom.
Didier