Eh, I'm not sure I would agree, about the 6502 specifically. It's a pretty bad match to C since e.g. it doesn't have a relocatable stack and common pointer-based operations are quite clunky despite the provision for several address modes. FORTRAN-like languages really do match quite a bit better. In a different way, so does FORTH.
Also, plenty of people did have fun writing assembly code for the MC68k, which is a 32-bit CISC architecture. It's really only x86 (and maybe VAX) that tends to be a bit clunkier.