Amazingly, they've all came out this century and I can't believe I'm leaving Seinfeld off of this, but......
1.) Breaking Bad - best show from beginning to end I've ever seen. Awesome premise, at least four complex, intriguing characters. Never bored.
2.) Game of Thrones - read all the books before it became a show and have been impressed with the HBO series. Nice recovery from a bumpy season 5 last year.
3.) Curb Your Enthusiasm - not one bad episode out of 80 or so made thus far. What other comedy show can say that?
4.) Sherlock - I binged watch the "miniseries" I guessed you'd call it and was captivated in each episode. Cumberbatch and Freeman both outstanding.
5.) The Wire - Yeah. I wanted to hate it because everybody was telling me how great it was, but it was a fantastic series.
I haven't seen The Sopranos yet. Honorable mentions would be Seinfeld, NYPD Blue, 24, The Americans, The Norm Show, The Office, Peaky Blinders, and Lost even though they lost their way at the end there.