The thing that bothers me about Quantum Leap’s ending is this:
If Sam fixes it so Al is reunited with his wife and all that and as a result the Project never happens - then how does Sam go back in time to fix everything?
[Action-movie-hero voice]
Ceejaytee, you fiendish villian! You won’t get away with this! The forces of good will put a stop to your nefarious plot!
[/Action-movie-hero voice]
Yeah, yeah, yeah. Point conceded re: deep-space franchise.
But I still loved the books. 
In order for the last episode to be considered “bad”, there have to have been some GOOD episodes. There were no “good” episodes of Gilligan’s Island.
And I watched every episode to make sure… 
According to the final episode, the entire Newhart series was all just a dream by Dr. Hartley, referring to the infamous “Bobby isn’t really dead, it was all just a dream by his wife” episode.
For that matter, what about the final episode of Dallas, which was yet another rip-off of It’s a Wonderful Life? Parts of it were funny (Cliff would have been President had J.R. not existed), but it was mostly lame.
I want a second vote, and it is: Twin Peaks. For a show that was so wholly weird, the ending where the demon possesses Agent Cooper leaves you wondering, since Cooper was the only person who really understood and had motive to chase the demon, what did the future hold? Cooper chasing his own tail. Yawn.
Ok, I knew about the dream in Newhart but I thought someone said the reference was to Dallas’ final show.
Regarding Dallas, the funny thing about Cliff being Veep and becoming President was that the episode aired within a week of Bush having some spell where Dan Quayle almost took over for a bit.