Dr. Who - but only the seasons with Tom Baker
Star Trek
Voyager
Deep Space nine
Next Generation - but only after season 3.

Lost in Space - always for a good laugh.
Space 1999 - first 2 seasons only.
Red Dwarf.
UFO.
X-Files - there were seasons where it was mostly about aliens.

Hey, is Farscape that aussie production, with humans and aliens on a planet with intrigue type things happening?