As with all lists like this, it is pretty subjective. Some of these shows I have never heard of, some I would like to see.
I have always really liked British Sci-Fi as they could do a lot with cheesy special effects but had a great story line and characters, along with some really good actors to play the roles.
Now while not strictly a sci-fi show,”The Avengers” TV show from England had it’s share of sci-fi themed shows.
I agree, there are a few I've been meaning to see, but never have. One that's been on my list (but I've been too busy, I'll probably binge-watch "Orphan Black" in a few weeks, when I take a vacation from work.)
But here are a couple of observations I've made from the list of shows that may note be quite as well known:
#40 - Humans - Great show! Can't wait for the next season! If you have Amazon Prime, you can stream it at no charge right now.
#33 - Man in the High Castle - Rather interesting, sometimes difficult to watch. You may need to watch the series more than once to "get it." Also available on Amazon Prime.
#18 - Dollhouse - Joss Wheedon did a great job here, though it's somewhat adult themed in some episodes.
#15 - Fringe - This show was a really wild ride here. I think they got notice the show had been cancelled, and they had to rush to tie up the loose ends. The first 2 or 3 seasons were awesome. Think of "The X-Files" on steroids.
#7 - Firefly - Joss Wheedon's MASTERPIECE. An awesome show, it's actually a SF show that's character based, and you will genuinely begin to care about the characters. Great dialog, and possible the best cast TV show since "Gunsmoke."
#3 - Battlestar Galactica (Reboot) - If you watch the mini-series and like it, you will LOVE the next few seasons! The first episode once the show was picked up, "33" is one of the most gripping TV shows I can remember. Great casting, great dialog.
Mark