The 6502 conversion was especially difficult, as the processor made use of some wacky analog tricks (like capacitive storage) which can't be represented in Verilog at all. The author of that conversion had to do a great deal of manual work to detect these features and convert them to digital logic.
http://www.aholme.co.uk/6502/Main.htm
But it does look like a lot of work, and it's not like you get especially readable Verilog from it.
Given other people have already built cycle accurate cores for these processors that are readable and maintained, it may not be worth it.