For me it would be shows that were designed for syndication -- you know, they go on forever and have very little overarching plot, so you can just pick up a random episode and watch it whenever.
Good examples of this are:
Star Trek (particularly TNG)
Hercules: The Legendary Journeys
Xena: Warrior Princess
Stargate SG-1
Heck, let's just list every sci-fi and fantasy show from the late 80's to the early 2000's.
There's a reason re-runs made up most of a TV station's daily airtime before reality TV came along. People will re-watch shows that were designed this way for eternity, given a lack of anything better to do than watch TV. Heck, the major kids' TV networks still work on this principle.