These have all been mentioned, but:
Arrested Development. The potential movie news made me giddy for days.
Carnivale. Incredible all around. Watched it all from Netflix in weeks, and couldn’t wait for the next season until I found out there was no next season.
Rome (admittedly this one probably ran its course).
Blackadder (likewise, and will never return due to Hugh Laurie’s success with House).
The next series of Rome wouldn’t have been too exciting, all the enemies were external when Octavian took over.
Blackadder had one of the best series arcs ever, from the idiocy* of the first season to the unexpected poignancy of the final episode of the fourth series. To do another season would almost certainly muck it up. That said, Hugh Laurie wasn’t a regular until the third season. While a lot of fans try to pretend the first season doesn’t exist, the second is pretty well-regarded.
Bob Newhart’s third sitcom, Bob.
Arrested Development was a show that was funny when it was fresh, it was already getting stale and the jokes were painfully repetitive by Season 3. I think that this show would have left it’s fan’s making excuses for it if it had stayed on the air.
To the OP, the question has two categories for me. Shows that were canceled too soon and shows that had a good run but are still missed.
Firefly is the biggest one in that first category. I can’t think of another show that I liked that much and had that much potential that died so quickly and unjustifiably. Someone needs to be blackballed from the industry for that decision. Drive was also one that looked like it deserved more love too. Fucking Fox.
The West Wing and The X-Files had a good run and probably outlived their usefulness but I still miss them terribly on Sundays and Wednesdays. I looked forward to them every week. Its going to be hard when Lost is over.
omgosh - I completely left off
My So Called Life
That was an awesome show.
Firefly
Keen Eddie
Is Life going to get revived?? I really enjoyed that one…
Usually, when these threads get started, someone always mentions the ones I want to submit. One has been mentioned: Freaks and Geeks. But I guess in a way it’s bittersweet because I love that show, but I guess I wouldn’t wanted to have seen it go downhill and then not like it.
The other one, that I don’t think I’ve seen mentioned yet is: Andy Richter Controls the Universe.
I would have been 28-31 from start to end. That show was such a gas! You can catch some of it on youtube, btw.
Firefly
The Dresden Files, for purely selfish reasons.
Parker Lewis Can’t Lose
Enterprise. Angel. I think they both got canceled at the same time just to piss me off.
One of us! One of us! One of us!
If it was still on now, it would be season six, I guess, and we’d be debating over when it jumped the shark, but fifteen episodes was too few, dammit, too few.
NFL Primetime.
It’s been a couple of years now and I still dearly miss the best part of Sunday afternoons. It was the perfect show between the morning and afternoon games, and the night game. **The Blitz ** has not filled that gap for me, sadly…
That show finally found a good storyline with the Anti-Tru, so I was disappointed when they canceled it. It had potential.
I wish shows like Angel, Veronica Mars, Carnivàle, Firefly, Wonderfalls and Dead Like Me (as long as Bryan Fuller had remained in charge) had run as long as possible, but the only show I really miss–even though it had gone downhill thanks to a cast of thousands, the absence of its librarian, the lack of Whedon’s attention, and the campy transformation of its bad boy vampire into Count Blandula–is Buffy, the Vampire Slayer.
I didn’t see anyone mention this one yet:
The Rockford Files
I “Nth” (both of which I discovered after they were off the air):
Arrested Development
Firefly
And I’ll add:
(the BBC version) The Office
Gervais has (so far) known to quit whilst he was ahead. I don’t think they could have run it further without it getting hackneyed.
I’d love to see Babylon 5 come back. I know it was only planned for five seasons, but I loved that series. I was amazed to see someone else put Misfits of Science on the list, because that’s one of the ones I thought of! From my childhood, I loved the Dungeons & Dragons cartoon. There were tons of shows I could mention from the SciFi channel that I wish they’d bring back as well.
A couple already mentioned:
MST3K
Futurama
And a new one:
The Critic
B5 overstayed its welcome by about a season, I could have done with a little less of Earth in S4 and the psychics in S5, maybe merge what was left of the two.