A.L.F.

Heroes. Super perfect with the motto "Save the cheerleader, Save the World"on the first season. Then, second season's quality went downhill and they had more seasons from there but they were garbage.If not for those problems, Heroes would certainly be the Top 1 super heroes series up to this day.

Jericho, sort of. It didn't really end in a cliffhanger, but I'm still not sure the alternative was any better. The first season introduced multiple intriguing intertwining plot lines. Then instead of cancelling it immediately, the show was given a shortened second season to wrap things up. Most open ends were closed in that, but in a very rushed and simple way. It missed a lot of opportunities to expand on those plot lines before closing them in a much more satisfying way.

And as a bonus answer, not a TV show but the Divergent movie series. When reading the books I was devastated by the ending and wondered how I didn't remember that from the movies. Then someone told me the movie series split the last book in two parts, but the second part got cancelled and thus the movie series ended halfway the conclusion of the series.

The Old Man

Agent Carter.

Ozark

The Cape.

Surface

The book of Daniel

Heroes

Lovecraft Country (There needed to be MUCH more!)

Lots of others 😔

The original lost in space tv show.

Dallas

Legends of tomorrow, alphas, ncis LA, ncis Hawaii, twin peaks.

NCIS New Orleans

Carnivale

Sopranos

NCIS Hawaii

Dirty Sexy Money.

Danish drama series called The Legacy (originally titled Arvingerne). What's double frustrating is there's a season 3 - but not available in USA, even to buy !!!

Forever
ALF
The Peripheral

Evil

1899 (Netflix)

deadwood got cancelled. thats a crime

The Peripheral

The sopranos... though I'm not sure they were cancelled... but they certainly purposely left on cliff hanger

Trump 2.0?

SURFACE -- which probably no one else remembers.