Everybody’s saying they immediately thought of Cheers. My first thought was The Partridge Family.
What?
Eight Is Enough. Diana Hyland, the original mom, died after one season, and Betty Buckly was brough in as the father’s new love interest, and eventually became the step-mom. It went on for about four years after that.
Dallas survived the death of Jock Ewing. It also survived the death of Bobby Ewing, except it was all Pam’s dream.
Yeah, but it’s just never been the same.
One of my favorite shows I now mourn for. The cast is still very talented, but without John Morgan’s writing it lacks the magic it once had.
“And lo, it came to pass, that Abraham dot com did take himself a wife. A fine strapping woman, known to one and all as the Amazon dot com…”
Please, God, let it die already!!!
Every soap still on the air.
Jeopardy survived the loss of Ken Jennings.
He became a star because of the show, the show wasn’t built around him. At this point, I think the only remaining original cast member is Noah Wyle (could be wrong about this – I stopped watching a few years ago – no, not because George Clooney left 
). Like a lot of 10:00 dramas, the show was designed around an ensemble cast, which gives the producers a lot of flexibility to change story directions with a changing cast. (Cf its predecessor in the Thursday-at-10 slot, LA Law; its original rival Chicago Hope; St. Elsewhere, etc.)
Didn’t the Charlie Sheen helmed Spin City hold up for a few years following the loss of Michael J. Fox?
Every soap opera has had numerous characters depart during it’s run - that’s what soap operas are.
Doctor Who, the entire cast changed numerous times. And it’s coming back … with a new cast.
Jonathan Creek lost Maddie.
I believe that the cast at the end of MST3K’s run was 100% altered from its initial state. Kevin Murphy was the longest on-camera veteran at that point, but he wasn’t the first voice of Tom Servo.
Actually, I was originally thinking SitComs when I asked the question, but I didn’t specify, so I thinking it is all fair game.
Bonanza lost Adam Cartwright, when Pernell Roberts left (IIRC, he wanted more money than they were willing to pay him). It later lost Hoss Cartwright when Dan Blocker died.
The X-files survived (for a few seasons anyway) after David Duchovny left (actually I think it died more due to the change in style than characters).
Tikster
Maybe he could take a hike and give the same boost to CSI Miami.
And I know you suggested only sitcoms but Roeper just isn’t as good at is as was Siskel. without him Ebert’s just plain annoying
The only “major” character to die in Farscape was P’Au Zotoh Zahn. All the others were story plot devices and cliffhangers.
Recurring characters who died were Talyn and Bialar Crais. You could make a case these were major characters, but I’m of the opinion only Moya’s crew counts.
In the 2-part series finale, they killed Jool and Ka’ D’argo. They don’t count as the series ended.
You are mistaken.
X-Files went off the air when Duchovney left. There were no seasons eight and nine. There was talk of a movie, but nothing ever came of it.
Shows with ensemble casts can change pretty easily. Shows that center around one or two people, however, rarely survive the loss of that person. Eight Simple Rules might still be in production, but how many people still watch it? How many people still care? X-Files tried to go on without David Duchovny, but it just couldn’t. Mulder was too important a character to do without. Stargate might struggle on for another season or two, but without Richard Dean Anderson I can’t see it surviving for long.
Yeah, just like when Flo left Alice.
I never saw the show, but didn’t Good Times survive the departure of the father? I only know him as Admiral Fitzwallace from West Wing, but I think they killed off his character.
Blue’s Clues!
The actor who played “Steve” eventually got tired of being known as “that loser, wussy guy from ‘Blue’s Clues’” and so left the show to start (I’m not kidding) a punk rock career! A new actor playing Steve’s “kid brother Joe” came in. I guess the show survived. I do recall that my nephews stopped watching the show about the time Steve left. But that probably has more to do with them getting older than to do with cast changes.