I have 3 very different favorites, any/all are my favorite show: Dark Shadows (especially the 1991 Revival), Beauty And The Beast with Ron Perlman and Linda Hamilton and the most recent is Lost. I remember getting so wrapped up in the mystery of the Island and its inhabitants. And no, they were not in purgatory--everything that happened, happened.

Most of people knows best shows like: Scrubs, Black mirror, Game of Thrones
But something great which is not that common knows and the older ones are:
-Oz (1997) - the best prison serie - hard and brutal
-Profit (1996) - this is probably first series where we have evil lead character and we love it

I like funny ones, I recommend "the big bang theory"

Derry Girls.

Most recently Prodigal Son, disappointed that it's not being brought back for a third season.

Smallville, watched the 10 seasons twice

The serie I watched the most times i Friends.

Breaking bad

Sherlock (2010)
Game of Thrones (2011)
Breaking Bad (2008)

Sopranos.
Still holds up.