At least half the shows mentioned were fantasy and not sci fi. The original Star Trek was really pretty good... I think it would hold up and it was Sci Fi and so was SG1.
When my son was about 11 we caught the second half of a Blakes 7 episode while waiting for Monty Python. We thought it was a joke but it became part of our Saturday night routine and we got into it. Really not bad once we figured out who was who and what they were about.