Well, being a fan of sci-fi, i have a huge collection of series... some of them was already cited but some other was not :
- Andromeda ( 5 seasons )
- Babylon 5 ( original : 5 seasons, Crusade : 1 seasons, 6 films )
- Battlestar Galactica ( TOS : 2 seasons, BSG 2004 : 4 seasons/few web episodes/films, Caprica : 1 seasons )
- Bionic woman 2007 ( 1 seasons )
- Earth Final Conflict ( 5 seasons )
- Farscape ( 4 seasons, film "The peacekeeper war" )
- Firefly ( 1 seasons )
- Harsh Realm ( 1 seasons )
- Heroes ( 4 seasons )
- Mutant X ( 3 seasons )
- Odyssey 5 ( 1 seasons )
- Outer Limits 1995 ( 7 seasons )
- Sanctuary ( 3 seasons )
- Space 1999 ( 2 seasons / 1 film )
- Space above and beyond ( 1 seasons )
- Stargate ( SC1 : 10 seasons, Atlantis : 5 seasons, Universe : 2 seasons, films )
- Starhunter ( 2 seasons )
- StarTrek ( TOS : 3 seasons, TNG : 7 seasons, DS9 : 7 seasons, Voyager : 7 seasons, Enterprise : 4 seasons, 10 films )
- Terminator The Sarah Connor Chronicles ( 2 seasons )
- The 4400 ( 4 seasons )
- The dead zone ( 6 seasons )
- V 2009 ( 2 seasons )
- Warehouse 13 ( 2 seasons )
- X-files ( 9 seasons )
... a total of 2469 episodes...
Have recently loose a harddrive with Blake's 7 ( 4 seasons ), UFO ( 1 seasons ), Red Dwarf ( 8 seasons ), and Doctor Who ( 32 seasons )... all UK sci-fi...
Pretty sure that there is more sci-fi out there but i don't have them ( and don't know them )...
For family viewing, Outer Limits is very good because it is not a series in itself but more a short sci-fi novel by episode... with different themes for each episodes ( http://en.wikipedia.org/wiki/List_of_The_Outer_Limits_%281995%E2%80%932002%29_episodes )... Andromeda is good too if you forget the last season... Babylon 5 is very good but not the Crusade series...