Lies, damned lies
Statistics. (Popcon only counts Debian users with an internet connection who explicitly opt in. Numbers in the easily accessible website may be larger than they appear.)
AMD64 (any 64 bit x86) is way in the lead. I am suprised to see i386 (32-bit x86 with x>=3) in second place. armel (arms slightly simpler than Pi v1) is third with powerpc right behind. Armhf (Pi V2, lots of cell phones and tiny 'desktops') is further down than I expected (I think Rasbian doesn't get counted). Next comes 'unknown', but I have no idea where to buy one. Plenty more choices available including 68k and Itanic. (Popcon has not been ported to Lunix (yet) so 6502 doesn't show up :-)