The X-Files! I’d fucking love it if they brought that back.
The Tick.
Nowhere Man
Human Target
Twin Peaks
Gargoyles(continued from before ABC ruined it)
Alas, Police Squad.
In Color!
Pushing Daisies was the first thing that came to mind.
They’ve been mentioned already, but Deadwood and Pushing Daisies are my choices, since they were cancelled before they were able to finish telling their stories. Any number of other shows I liked are gone, but I don’t mind if they had their run and got to have a proper finale, or if they didn’t rely so heavily on an overall story arc that was bigger than an episode or even a season. These two were especially frustrating because it felt like I watched three-fourths of a really great movie but never got to see the end.
Same here. Sometimes I’ll re-watch an episode or two from Season 1 and it’s such an original, visually interesting, densely plotted show. In a way I guess it’s amazing they even made it to S2!
All of the shows I would have listed have already been mentioned except for one: I may be the only person in the world, but I loved The Sarah Connor Chronicles and was devastated when it ended. (Well, “devastated” is hyperbole. It was only a TV show after all. On the other hand, I do still have a music video on my iPod created from the show).
I’m amazed that others mentioned Keen Eddie before I got to it. I didn’t think anyone watched that or cared about it. I have noticed that the shows I would really love to have back tend to have actors in common: Mark Valley was in both Keen Eddie and Human Target; Chi McBride was in both Pushing Daisies and Human Target; Summer Glau was in both Firefly and Terminator: The Sarah Connor Chronicles. Note that I think Dollhouse was on just about exactly the right length of time and The Cape was awful no matter how much Summer Glau there was.
Rome
Firefly
Carnival
Deadwood
Pushing Daisies
Northern Exposure
In that order.
Pushing Daisies
Better off Ted
Dead like me
Firefly
and yes, I want the Eureka cancellation revoked 
I might have to agree with this because you’re right about the finding the audience thing… I’ve never heard of it.
Clone High is a good suggestion. It ended on a cliffhanger, it had good quality throughout, and since it’s animated you don’t have to worry too much about the actors having changed their looks.
Firefly
Keen Eddie
The Adventures of Brisco County, Jr
Johnny Quest
Andromeda
Wiseguy
Benny Hill
I’ll second the vote for Sarah Connor Chronicles, and millionth the vote for Firefly.
Sarah Connor was a muddled mess in the middle, but then ramped up into a surprisingly engaging show, just in time to get axed.
And Firefly was Firefly.
I wouldn’t be shocked if this gets a “reboot” in a few years. It’s going to sound crazy but I think all we need is a strong economy again. In a strong economy when people don’t have as many real world things to worry about, conspiracy shows give people made up things to worry about. That’s why, I think, The X-Files was so perfectly timed in the mid 90s. When times are bad, all that stuff seems just silly.
Mystery Science Theater, with Mike and the Mads.
“Eddie’s London is no more.”
– Eddie Arlette
Dear lord, I have a huge list of these.
Dead Like Me
Twilight Zone*
Outer Limits*
Stargate SG-1 and Atlantis
Married with Children
Justice
Tru Calling
My Name is Earl
The PJs
Gargoyles
X-Men (before they changed animation style)
Recess
Weekenders
Beverly Hillbillies (not sure how this would work in today’s world)
Justice League Unlimited
Boondocks (not sure if this one is canceled or not)
X-Files
Millennium
The Lone Gunmen (Would’ve worked much better if they hadn’t made it a comedy show)
Dharma and Greg
Mama’s Family
I could keep naming, but I think that’s enough.
*The original series of both. The series from the 80s and late 90s were garbage for the most part.
Thanks for reminding me of Matinee at the Bijou which became a Sunday morning must-see for my now-grown son and me back in the 90’s. It would be so easy to bring back.
The Secret Life of Machines.