I don't see the reason for the automatic qualification of "until 1985". That's really damning Trek with faint praise, isn't it? For one thing, there were hardly any serious, legit, American SF series before 1985. Stacking original Trek up against a dozen tacky (but sometimes fun) space adventure shows, some meant more for children probably, sort of misses the point of what Trek is. Is it better adult science fiction drama than Land of the Giants? Well of course, let's move on...
Original Trek is clearly the best for me, no time limit necessary. The only real competition would be Babylon Five, DS9 and Outer Limits. Honorable mentions to The Invaders and year one of Lost In Space, and Time Tunnel.
Talking about British shows, 1970s Dr Who and Blake's Seven were brilliant, and year one only
of Space:1999. Eliminate that second season of Sp:99 (which on its own would be in the running for worst
SF series ever...) and you have SF just as it needs
to be done on television. It's about time hasty viewers stopped dismissing year one, just because they associate it with that bastrdized second season.