I was pretty happy with these endings:
DS9 (although it did continue in novels)
Voyager (continued in novels)
Dollhouse (it continued in comics)
Buffy (continued in comics)
Angel (continued in comics)
Farscape: PK Wars (continued in comics)
Smallville (continued in comics)
I think Sanctuary ended in a way that was pretty good, but I would gladly watch or read a continuation of the story
The 4400 (continued in novels)
DS9 and Babylon 5 and Voyager didn't get cancelled early. B5 was always planned as a 5 year story arc, and in fact, TNT wanted another season, and the actors were also interested in another season.
VOY and DS9, I don't think there was ever plans to go beyond the 7 years that TNG lasted for, was there?
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?