I had hill street blues in my head when I wrote that, lol.
But theres a big gap there. And Sopranos and Sex and the City are the ones that made the big money. But even then, HBO had to do a bunch more series' before cable got on board finally. You can probably throw 24 in there as finally tipping the scales for execs dragging their ass and content that tells an actual story.
Sopranos blew the doors off with ratings and set things in motion. But Milch has hung around. See Deadwood, John from Cincinatti (WTF???), and Luck.
Also, I'm not a big Gary Shandling fan, but chroniclers of the Golden Age of TV we're living through give credit to the Larry Sanders Show and lots of other forays into original programming HBO was farting around with before it struck gold. And you really have to give them credit for that no matter if you hate pay channels. I GOT (no pun intended) HBO because of the Sopranos.
Their pedigree is to this day hard to argue with:
Their early comedy shit
Larry Sanders
Oz
Sopranos
Sex and the City
Six Feet Under
Rome
Deadwood
Carnivale
Life and Times of Tim (where you at Lance)
True Blood
Big Love
Game of Thrones
Enlightened (underrated, I'm told)
Curb Your Enthusiasm
Their later comedy shit (Ricky Gervais stuff, Life's Too Short)
True Detective (starring Alexandra Daddario nude)
Veep (I love Armando Iannucci but Veep is kind of dumb to me)
Silicon Valley
I'm sure I'm leaving a lot out, but they still set the bar