I thought Masks and The Royale were ok episodes. Nothing special, but not bad, I could rewatch either and enjoy them. I don't remember much about Threshold, I think I only saw it once, but I remember thinking it was bad. I liked Genesis, I thought it was an interesting episode. The Way to Eden just annoyed me. I'm not a fan of characters like that (i.e. hippies) so I just wanted them to get thrown out of an air lock the entire time. Its not the worst TOS episode by far, but its pretty bad.
Sub Rosa is probably one of my top 10 most hated ST episodes. I don't think it had one redeeming feature, although there were a few episodes worse than it in the franchise. I always hate the romance episodes. I am fine with episodes having some romance, like DS9 episodes with Sisko/Cassidy or Worf/Jadzia having screen time, but episodes that are almost fully devoted to romance/relationships always sucked (Someone to Watch Over Me
being the worst, and probably in my top 3 most hated ST episodes).