I think to be fair, the vast majority of the episodes should have aired in this decade. If you love LOST, please realize almost all of it aired in the previous decade.
My list would include the following shows:
Game of Thrones - yes, the ending was tough, but for me, the final 3 episodes were the only drop off. I kept with it longer than some. Still, it does hurt that the ending was rushed and felt put together incompetently.
**Gravity Falls
** Outlander - why does this show get so little love from critics and awards?
Hannibal
Westworld
**The Leftovers **- just watching the finale again(watched it all when aired). It really is an amazing and touching show.
The Expanse
**
Black Mirror **- less great lately, but those first two series were great
**Twin Peaks - the Return **- what a mess, but when it hits big, still one of the best shows. Episode 8 might be the best episode of TV this decade.
Taskmaster
Community
The Good Place
Unbreakable Kimmy Schmidt
Blunt Talk
Moone Boy
Detectorists
Person Of Interest
19-2
Unforgotten
Daredevil
Jessica Jones
Community So many of the best episodes ever.
Stranger Things: Perfection
Good Omens: So well done
The Good Place: This show is brilliant & funny.
The Marvelous Mrs. Maisel
The Daily Show with Jon Stewart
Last Week Tonight with John Oliver
I discovered it when it was about on series 4, after YouTuber Tom Scott listed it as one of his favourite shows, and I had no idea of its existence. I couldn’t imagine how it could be such a big deal, until I instantly fell in love with it after sourcing the first episode. Spectacularly simple idea, with cunningly crafted tasks, and, most importantly, perfectly cast hosts and contestants.
The season with Rhod Gilbert as a contestant might be the funniest comedy panel show type thing you will ever see. Honestly, it’s too much laughing for me sometimes.
I don’t watch sitcoms much, so I decided to make a Top Twelve list for dramas. Ranked.
Halt and Catch Fire
Luther
Game of Thrones
Succession
Better Call Saul
Treme
The Night Of
The Expanse
The Americans
The Leftovers
Breaking Bad*
Patriot
I doubt many would agree with my number one, but I think Patriot is one of the most unusual, funny, unique, moving and just flat out entertaining shows I’ve ever seen. Writer/director Steve Conrad and lead actor Michael Dorman should have won a bunch of awards for this collaboration. 10/10, will watch again.
Using the criteria in the OP, 42 of the 62 episodes aired this decade.
I can’t really vote for “best,” but in terms of what TV shows have actually held my interest long enough that I was able to watch through their run, there’s only a handful that have succeeded for me this decade: Crazy Ex-Girlfriend, Barry, and Archer. I’m not sure there’s really any other series that was able to hold my attention. I did enjoy It’s Always Sunny in Philadelphia, but most of the seasons I loved the most were last decade, and I haven’t even bothered to watch the last two or three, as I feel they just ran out of gas. I was also really getting into Good Girls Revolt, but they canceled it after one season so, oh well.
My list certainly isn’t going to me definitive, since I don’t have anywhere near enough time to watch All The Shows (I’ve never seen Game of Thrones, for example, so I have no opinion of it). But that’s true of all of us, so, of the shows I have watched here’s my top 10.
Chernobyl, albeit a mini series and not a full multi season series.
Boardwalk Empire
Stranger Things
Fargo, albeit more a series of mini series than one series
Bates Motel – A rather underrated show I thought was really good, especially the last two seasons.
Unbreakable Kimmy Schmidt
Orange is the New Black. It may have faltered a bit in its later seasons, but it picked back up in the last one and overall one of my favorite snows of the decade
Marvelous Mrs. Maisel
Better Call Saul
The Americans – the one show in recent memory I always looked forward to seeing the next episode.
The top three are definitely in order with The Americans as my all time favorite. The rest are pretty much in no particular order other than the order in which I thought of them.
Honorable mention to Breaking Bad and Mad Men, although it’s debatable whether they’re of this decade or the previous one, so I didn’t include them in the actual list. The majority of the episodes of both series aired this decade, but the first few seasons aired the previous one, so I don’t know how were defining “vast majority”.
They have just started putting it officially on YouTube for international viewing. Limited episodes, maybe for a limited time, and thus far only season 2, but that shouldn’t be an obstacle.
Mad Men ran from 2007 to 2015, so I guess that falls in the “majority of episodes aired in this decade” category. Arguably it fails the “**vast **majority” criterion. Anyway, in my opinion, that show outruns any of those previously mentioned in this thread.