Worst multi season series ending of a good series:
DEXTER
No competition.
Except maybe "The Sopranos."
I think after they introduced the Trinity Killer the series struggled, especially with Rita dead and Dexter more or less kind of in arrested development.
The last season was absolute garbage that chose tawdry symbolism over coherence and substance.
I agree, it was a pitiful end to what was a great show.
Umm, remember Lost?
I don't even remember that one.
The two classic series endings are Newhart, where the whole series turns out to be a dream that the Bob Newhart of his other series had, and St. Elsewhere, where the whole series apparently turns out to be an autistic child's fantasy. The first was brilliant. The second awful.
I do remember the finale of Michael C. Hall's other series Six Feet Under, which showed how the characters in the series would live and die in the future on a time scale stretching far into the future. It was also very clever, but a little too dictatorial for the show's creators to assert their authority in that way.
The ending of The Sopranos was a classic let down, but it got people talking, which was probably the idea. I wasn't impressed by the ending of Man Men either, but I had a lot of problems with that show.