Do you mean serious SF that is very serious or making a point? If so, the 1960-70s is probably your Golden Age.
"Doomwatch" was a British SF series about pollution and the environment (from the 1970s!). Some of these are relatively well known, but you could look at films like "The Andromeda Strain", "Westworld", "Soylent Green", "Phase Four", "THX1138", "Fahrenheit 451", "Silent Running", "2010". If you dare sit through the very, very, heavyweight Russian stuff like "Stalker" or the original "Solaris", go for it. The original version of "Rollerball" is pretty good.
* * *
If you just want non-comedic, obscure SF that's just entertainment, I know a few old, mostly British TV series. Bear in mind British SF tends to mean low production costs, so they often look pretty shoddy in comparison to US stuff of the same period.
There are obvious classics like "UFO", "Space 1999", "Blake's 7" or "Sapphire & Steel" (the last actually for children's TV but well worth a look). In both TV and film, check out the Quatermass stuff. There was a good modern-day vampire thing that only ran for one series of 6 episodes or so called "Ultraviolet" (nothing to do with the recent movie). "The Prisoner" is a massive classic, and probably SF, although hardly obscure. Maybe not so well known now, there was the US TV series "V".
There's some other little-known TV stuff of variable quality like "The Tripods", "Day of the Triffids", "The Invisible Man" from the 80s, but I'd leave them until last.