best TV detective series

[Executive]

My favorites are from the 1970s primarily.  Columbo and Cannon were the best, as were Barnaby Jones and The Streets of San Francisco.

Of course that's private and public cops.

[quasomb]

Pr. Robot is quite enjoyable. It's not too long and easy to digest

[Slobodancovek]

For me the best is Italian TV series based on a novel.

Inspector Montalbano https://www.imdb.com/title/tt0920489/
The Young Montalbano https://www.imdb.com/title/tt2259665/

It was aired on BBC, so you can find it with hard-coded English subs, which is good because there are no synchronization issues. The translation is not the best, but it is much better than in any other subs available.

[iptInGUA]

Man that's a tough one, considering the 70's were filled with nothing but.

Personally I'd have to say, Mannix, Baretta, Rockford Files.

...tough one.