Carnivale needs more love.
So good, and sadly too shortlived. Anybody who likes a little art in their HBO style TV,
Carnivale is for you. Beautifully shot, extraordinary characters and an engaging story.
Also,
The Last of Us is some great TV. It's a bit different than other HBO shows, but still great.
Aside from that recommendation, everybody else has probably already touched on, but my opinions, since I'm sorta bored at the moment:
The Sopranos is listed by many as the greatest TV show ever for a reason. It's that good.
The Wire is great, but has one pretty weak season and it's early on and was tough for me to get through.
True Detective Season 1 is amazing. Season 2 is fine, and I thought was good to start, but lost me by the end.
Game of Thrones is classic fantasy TV. If you like Fantasy as a TV or movie genre, it's about as good as it actually gets, despite the flaws of the later seasons (Season 6 was good, people forget and lump it in with the last two, which while entertaining, aren't particularly "good")
House of the Dragon seems good so far, I dig it.
Oz was a good show, but got a little redundant as it progressed. Still worth a watch, no question.
Six Feet Under was brilliant TV for it's time and holds up today
His Dark Materials is a really great show if you want to avoid the gratuitous sex and violence of every last one of the other shows on HBO. I actually really enjoyed this show. Very different.
The Righteous Gemstones is pretty damn funny. Not for everybody for sure, including me, but I laughed a lot before getting bored of the story itself.
I don't do political or business office shows at all, so I haven't seen a bunch of the well respected shows in those worlds. I also haven't seen Deadwood, which seems right down my alley, but damn... just listing all of these above makes me feel like I need to get out more.