From my 15 yr old perspective back in the 1960s, having gotten into visual science fiction at 8, Lost in Space had Zorro, Timmy's Mom, Danny Thomas' daughter, that creepy kid from all those Twilight Zone episodes, a hot looking Scandinavian chick, and the coolest robot since Forbidden Planet (both by Bob Kinoshita). But it started shifting focus to Smith and the Robot as early as the 12th episode, and I quit hoping for anything better out of it. I watched the show for the hardware, which was often the best thing about Irwin Allen's sci-fi shows.
Star Trek had actors I was generally unfamiliar with, but better stories, and special effects concepts that I didn't know about (bluescreen/optical printing). It took a couple of weeks for me to really get into the show since I didn't like the alien makeups compared to what The Outer Limits did 3 years earlier.