I've have not yet had the opportunity to see or play a Skateball, Flash Gordon, Mystic or Spectrum so the point made above about games that are not popular or common is correct for my voting here. I have played Paragon so little and so long ago, I no longer have any idea how it plays.
Thanks for attaching the video of Skateball. I am watching it now and wishing I had access to all of these games. How many of the top SS Bally's are at the Pinball Hall of Fame in Vegas? Maybe I need to make a trip out there.