Just because of the sheer volume involved, ranking TV is really, really hard. Alan Sepinwall and Matt Zoller Seitz, who are two well-known TV critics, put out a book about 5 years ago (TV: The Book) where they had a good discussion about the merits of comedy versus drama, older shows versus new shows, etc. For the record, their top ten (which included comedies, but also focused on North American TV) was:
1) The Simpsons
2) The Sopranos
3) The Wire
4) Cheers
5) Breaking Bad
6) Mad Men
7) Seinfeld
8) I Love Lucy
9) Deadwood
10) All in the Family
Somewhat unsurprisingly, this list is identical to mine, except that it includes comedies (oh, and it has Deadwood in the top 10 instead of an honorable mention).
EDIT-
And I looked it up- after accounting for the comedies issue, my list ended up looking like this:
The Leftovers- not included because it wasn't complete at the time they wrote the book (2017) (they used that criterion too!).
Rectify- not included because it wasn't complete at the time they wrote the book (end of 2016).
The Americans- not included because it wasn't complete at the time they wrote the book.
Sopranos- #2
The Wire- #3
Halt and Catch Fire- not included because it wasn't complete at the time they wrote the book (2017).
Mad Men- #6
Breaking Bad- #5
Buffy/Angel- #25
The Shield- #13
So if you remove the comedies (1, 4, 7, 8, 9, 15, 16, 17, 18, 19, 21, 22), then all of my picks that were eligible were some of their top ranked ones.
Here are the revised top 15 dramas by their criterion (drama only):
1) The Sopranos
3) The Wire
3) Breaking Bad
4) Mad Men
5) Deadwood
6) M*A*S*H*
7) Hill Street Blues
8) The Shield
9) The Twilight Zone
10) X-Files
11) Twin Peaks
12) Lost
13) Buffy
14) Oz
15) Friday Night Lights