I happened to be looking at the NYSDOT Scenic Byways site for something and noticed that on their
byways list there's a link to a (slightly outdated, judging by the Robert Moses State Parkway)
parkways list, with a note that the are listed in the regulations of the Commissioner of the Office of Parks, Recreation and Historic Preservation. This list does include the NY portion of Palisades Interstate Parkway (notably, it does
not include the NJ portion in the mileage total), if that affects the debate on which system that should be in. A couple of other interesting findings:
-The Bay Parkway is listed as being its full length to where it turns around, not just the portion between the Meadowbrook and Wantagh.
-Ocean Parkway in Brooklyn is not listed.
-There is a Montauk Parkway included; not sure what that is referring to. Google Maps just has it for the eastern portion of Montauk Highway (NY 27).
Some interesting food for thought.