I’ll agree with this! Every time I watch the show I think “This show is never not funny!!”
I’ll add in Bob’s Burgers, too. It makes me think the same thing.
I’ve tried and I can’t remember a bad episode of Arrested Development from the original run. Likewise Fawlty Towers as mentioned above.
I came here to mention Fawlty Towers. Cleese deliberately stopped making it in order to maintain consistency. Unlike Monty Python, which definitely went downhill in its later series.
I agree with several of the shows already mentioned, but I’ll add* Numb3rs* and Rick and Morty. I’m only mentioning shows that I’ve seen every episode of.
For consistency, it’s hard to beat Scooby Do. Every episode was nearly identical!
Wait, that’s not Gatopescado… tackle him, Shaggy; you sit on 'im, Scoob! I’ll just… remove this… mask. And, it’s old Mr. Zotti!" “You mean, the caretaker from the Haunted Barn House?” “The allegedly Haunted Barn House, you mean! I guess someone got caught… with their barn door open!”
[cue laugh track]
The problem is, any episode with Kari Matchett beats any episode without her.
Except the one with the gypsies. “Through the forest, wild and free…”
Justified
Deadwood
Larry Sanders
Also, my memory of Southland was that it was consistently good.
I’ll second The Expanse, which has been outstanding.
You have to look at the low end for the most consistency. Take something like Joanie Loves Chaci, every single episode sucked horribly, no exceptions. It’s difficult to beat consistency like that.
“And I would have gotten away with it, if it weren’t for you meddling Dopers!”
My thing with NCIS is, while I didn’t exactly like DiNozzo, I can’t fucking stand Wilmer Valderrama as a generic cop (Was Jon Seda unavailable or something?). Valderrama is a comedy god, but that newfound musculature is wasted on him. And I have come to dread anything with the words “guest-starrting Scott Bakula.”
One show I loved from start to finish was The Closer. I love that the entire cast (except for Kyra Sedgwick) were veterans of classic cop show procedurals. And while posterity may blanch at their treatment of transgender issues, I thought they handled those two episodes with at least an honest cop’s-eye view of the issues involved.
The Detectorists. Not a single foot wrong.
I’ll second Justified. I can’t think of any episodes that I would skip on a rewatch.
There were definitely a number of episodes where they were just filling time with anything they could think of, because they’d run out of ideas.
Really, the show peaked at the end of season 2 with the big contest between House and Foreman. The setup of having Foreman get done in by a laughing cop was a bit silly, but otherwise that set of episodes was probably the “real” end of the show. Everything after that was just continuing to make more of the show for the bux.
I’d say that the whole battle between House and the one policeman was a pretty poor excuse of a plotline. The episode where he’s on a plane and everyone’s suffering from mass hysteria-turned rash was pretty bad. I’m sure I could think of a number of other one-off episodes that are pretty skippable.
Then let’s add Small Wonder! 
For most consistent, one I haven’t seen mentioned in sit-coms, is SOAP.
That’s too bad. I saw the first half dozen episodes and I thought it was pretty dull; I was hoping it might get better over time.
From Inspector Morse through Lewis and now with Endeavour, the mysteries based on the characters of Colin Dexter have been great TV. The series began in 1987 and is still going strong with outstanding acting and writing. Poor Oxford has had more than its fair share of multiple murders and so many erudite killers. But it sure is fun watching them get caught.
Oh yea! How could I forget about Justified!? One of the best.
Agreed.