20. Vega$ (ABC)
When this Aaron Spelling-produced drama debuted in 1978, it had everything a quality detective show should: a sexy leading man (Robert Urich as private eye Dan Tanna), a city full of sin (Las Vegas), and the kind of car that still gets mentioned anytime someone writes about the show 30 years later (a red Thunderbird). It also had a dollar sign instead of an 's' in the title. Which is awesome.
Seasons on DVD: None

NOTE: For this gallery, we used the 1978-'79 season ratings from The Complete Directory to Prime Time Network and Cable TV Shows