The examples of the latter are endless. Aside from XF, I am looking at you, MA*S*H, ER, Gilmore Girls and pretty much every other show on the planet. One show that went out on top (well, for the most part) was Life On Mars. Two seasons of utter perfection. Breaking Bad is another. But these are few and far between.
Doctor Who is in a category by itself. Yes, it's been on for years. But let's face it, people. it really is a brand new show each time they change the lead. I know they claim it's the same person, keeps the same personality, blah, blah, blah. That's true in a very loose sense. But each actor brings their own personality to the role. Plus, they are apparently bad with continuity, so there's not even that.
Side rant: Let's not get into the fact that in true, British, PC-fashion, the next Doctor HAD be a woman. Not just happened to be a woman because of the strength of her performance or passion for the role, but ONLY to satisfy the PC crowd/rabid feminists who claim to be oh-so-oppressed because a man played the role for however many decades. What's next? A gender bending Sherlock Holmes? Perish the thought!
ETA: Oh, and Babylon 5! Here is a unique example of a show that very easily could have ended prematurely due to major issues/behind-the-scenes drama such as cast members leaving, cast member health/drug/alcohol issues, and zero support from the networks. I'm telling you, back in the Dark Ages of only three networks (yes, kids, the stories are true!) I knew every show out there. I never even heard of it of until I got online on LiveJournal, and that was not until 2002. It's almost like the network(s) wanted it to fail, which makes no sense even from a business standpoint.
The reason it hung on was partly good fortune, rabid fan devotion, and word of mouth evangelization, and partly excellent writing and commitment from the creator. The creator had a set story arc in his mind with beginning, middle and end. He was able to sell that to the network(s) and so they kept hanging on, season by precarious season, despite poor ratings and no one being able to even find the darned show because the channel, time and hours kept being changed!
He is also a person of principle. He had a deep loyalty to the cast and crew and wanted to keep them working because he believed in this story, he wanted them to believe in it as well. and he just cared about them. It really is a wonderful story. I never knew the extent of it until just a few years ago, when information came to light about the severe mental health struggle of one of the lead cast members. I don't mean mild depression or "anxiety" (since when did that become a mental illness?) I'm talking about seeing hallucinations and hearing freaking voices. I cannot imagine how terrifying that must be. Worse, there were times he had to film scenes about having hallucinations and hearing voices. I believe JMS wanted to change this, so as not to put this poor man through what must have been hell on earth. But he kept on, not wanting to jeopardize the show and have all those people lose their jobs - especially the crew, who are often paid very little compared to the "stars".
JMS promised to not reveal this secret until this man's death. He kept his word. We're talking years.
That is rare in the world, and especially in this particular business. I think the whole world was stunned. Outside his family, no one knew. It made me so sad to know that this man kept this pain hidden all that time. He didn't want to burden his cast members or risk the show being canceled by the networks. He only told the creator because he was having such a bad time and couldn't hide it anymore. I'm guessing people even thought he was on drugs or something, when that was not the case at all. He had to let them go on thinking that because there was such a stigma about mental illness that it's realistic to think the show might have been canceled. He was more concerned about others losing their jobs, than he was about losing his own job. So he suffered in silence, while keeping up the grueling schedule of a lead of a 1 hour television show.
In so many respects, Babylon 5 was something special. This is that rare situation where the writers, the actors, and everyone involved with the show knew they had something special, even as they were doing it. That doesn't often happen. It's often impossible to see things objectively while you are in the middle of it.
While it's not perfect in the sense that there were some abrupt endings to characters and story lines, it really was the best outcome possible under these difficult circumstances. I never knew the extent of it all until long after I'd watched it the first time. I've come to hate behind the scenes drama. It takes away from my enjoyment. This is due in no small part to stellar actors. They took what could've been a corny, cheesy Star Trek knockoff and turned into high tragedy. I thought maybe my first viewing was colored by the endless praises of its fans, which fans were nearly religious in zeal. I don't think that's true. I watched it a second time and it was just as brilliant. It has one of the most beautiful show conclusions I've ever seen. In fact, I can't think of any show that comes close, except maybe Life On Mars. M*A*S*H might come in a distant second, although both the show and the finale were way too long. By S11 it had become The Alan Alda Show, and All Melodrama, All the Time.
B5 stands alone.
I'm pretty convinced most regular shows should go no longer than 5 seasons. That's about how long the writers seem to have fresh ideas and the actors have an interest in the roles and the story. After that, everyone gets tired and bored. Once they start with flashback episodes, clip shows, or (God forbid!) introducing babies or small kids, you know they've run out of steam. I can't say I blame them. Network shows with 22-24 episodes per season are grueling for those who make them. We really don't realize how long it takes to produce something of even marginally good quality. These people work 12-16 hours a day, often in bad weather, sick, injured, away from families/in the midst of family / personal problems. etc. And that's just the "stars". The real heroes of shows - stunt doubles and those behind the scenes - work even longer hours, for crap pay, and get very recognition or respect. If they're lucky, they might get a mention about a technical award. And even those are often given off-screen, because most people don't care. I care! I'm one of those nerds who sits through the entire credits of movies until the screen goes black. It's a leftover from when I was a kid. When I was little, I dreamed of one day seeing MY name in the credits, if even in tiny print, for the most un-glamorous contribution!
Netflix shows should be 1 season, and 2 only in very rare instances. Those now raised on Netflix binge-watching have very little patience for anything more than that.
And whether it's TV or movies, I think everyone on the planet is tired of sequels, prequels, revamps, reboots, remakes, reimaginings, and book-to-movie offerings that are often crappier than the crappy books upon which they're based.
Whew, that was longer than I intended. Can you tell I am passionate about my story-telling?
What say you?