I too liked:
Six Feet Under
Breaking Bad
Might add:
Sopranos
The Lost (but that jumped the shark)
I may come back to add more...yup, Deadwood was good too (but not my top 3) and The Tudors
I didn't watch BB until 2016ish. Watched the Sopranos late too.
So for me as I watched in real time...
The Lost, Six Feet Under and The Tudors were shows I couldn't wait to watch every week.