Terminator: The Sarah Connor Chronicles
Terminator: The Sarah Connor Chronicles (TV Series 2008–2009) - IMDb
Never got to finish season two before they killed it was better than and built upon all the terminator movies.
KyleXY was another cancelled good one though they did spend the first few seasons super slow and teen puppy love, pity that as soon as the ramped up the pace.. show got killed.
Here's a show that ended on time but.. could of had way more seasons
watch this if you have time
The Lost Room
The Lost Room (TV Mini-Series 2006) - IMDb