Long time Space:1999 fan here. I've been thinking about this a lot over the years and I agree with you; the show is best looked at as The Twilight Zone in Space. Well - first season anyway. You REALLY have to pick through the dung of second season to find a few "well, that bit was alright" moments.

I think the show worked best when it was a review of variations of loneliness.

* Dragon's Domain - Tony Cellini is burdened by the loneliness of a demon no one else sees. * Guardian of Piri - John Koenig is surrounded by the best of the best in his senior staff. But under the "spell" of the Guardian, he has disagree with all of them and make some very lonely decisions. * Voyager's Return - Ernst Queller is burdened by the memory of his mistake many years ago with development (and many deaths) of the Queller Drive. And it comes back to haunt him in real life, not just his imagination. * End of Eternity - The alien Balor shows us that immortality could be the ultimate form of loneliness.