I enjoyed UFO and Space:1999 (to a degree), but their production values and episode plots seriously paled in comparison to Star Trek. Space:1999 had a lot of potential, what with Brian Johnston and Derek Meddings working their SFX and model magic. But Anderson once again stumbled with the premise, at first trying too hard to appeal to the intellectuals, then swinging too far in the other direction of appealing to the youth craving easy to digest entertainment (partly due to Fred Freiberger).
and Space: 1999
had lots of potential. I was an Anderson fan before kindergarten, being turned on by Thunderbirds
and Captain Scarlet.
is an especially sad case, since its second season provided an opportunity for improvements, but the writing was (for the most part) so much worse than it was in the first season, that the show had nowhere to go but off the air.
I think part of the reason why such a strong fan base built up around Star Trek was the very lack of alternative sci-fi TV programs that could match it.
I agree. With respect to Anderson, the Supermarionation shows were pigeonholed, at least in the US market, as children's shows, but neither UFO
could compete with Star Trek.