Not sure if they got cancelled, they just stopped production:
Kenan and Kel
All That (pre-2000)
The Secret World of Alex Mack
Are you Afraid of the Dark?
Malcolm in the Middle
The Beautiful Life
Futurama got cancelled? I thought they were starting a new season?
" Like people have already said Arrested Development, Futurama, Deadwood. But i also say the original Star Treks, who knows what else would have happened during those lost two years of exploration. "
While it would have been nice to have more seasons of the original series, there is a chance that their existence would have actually prevented the explosion of Star Trek movies and series that occurred in the 80s and 90s. Since the series only lasted 3 years and was canceled as a relative ratings "failure", it was cheaper to purchase for syndication than "successful" shows. Because they were cheap, the syndicated reruns were on all the time in the 70s at a time when television markets only had 4-6 channels (affiliates for the three networks, a PBS, and one or two independents.) This built the core audience for the franchise and led to the commissioning of the movies and eventually to The Next Generation. It seems very possible that a moderately more successful original series could have simply faded away at the end of its run.
Deadwood, fer sure. I've reconciled myself with the ending and the way it fits into history, but it could have been so much more.
On the flipside, at least I don't have to see any more of Timothy Olyphant's weird do-not-swing-your-arms-dammit walking style.