Quantum Leap (NBC)
Air date: 5/5/1993
Until they catch the finale, viewers of Quantum Leap assume they're watching a sci-fi spin on the story of purgatory. If you paid attention to the protagonist's name, Sam Becket (Scott Bakula), then you might have gotten a clue as to the true nature of the story being told, and it's far from an uplifting tale. This wasn't a one hundred episode long tale of redemption, but a snippet of a man's infinite Sisyphisian labors.
Just how the characters in Waiting for Godot never stop marking time before Godot's arrival, Becket never gets to go home. It's not that a sentimental ending would have been welcome, but watching your protagonist compare his life to that of a priest only to conclude, "At least a priest can quit" is pretty much the opposite of a feel-good ending. Just in case you had any hope left after that, the producers offered one last title card. It read: "Dr. Sam Becket never returned home."