Star Trek: TNG http://graphtv.kevinformatics.com/tt0092455
Deep Space 9: http://graphtv.kevinformatics.com/tt0106145
Enterprise: http://graphtv.kevinformatics.com/tt0244365
Or in each season
Game of Thrones: http://graphtv.kevinformatics.com/tt0944947
Or took a while to hit their stride, then left right after the peak Seinfeld: http://graphtv.kevinformatics.com/tt0098904
Had a story arc: B5 http://graphtv.kevinformatics.com/tt0105946
Or were clearly failing:
Andromeda: http://graphtv.kevinformatics.com/tt0213327
Sliders: http://graphtv.kevinformatics.com/tt0112167
Futureama: http://graphtv.kevinformatics.com/tt0149460
Or are experiencing a revival
http://graphtv.kevinformatics.com/tt0121955
I wish this could be correlated against ratings data.
And or course: Dr. Who http://graphtv.kevinformatics.com/tt0056751
edit:
Also Law & Order http://graphtv.kevinformatics.com/tt0098844
and Law & Order SVU http://graphtv.kevinformatics.com/tt0203259
and Law & Order CI http://graphtv.kevinformatics.com/tt0275140
and the Stargate series
http://graphtv.kevinformatics.com/tt0118480
http://graphtv.kevinformatics.com/tt0374455
http://graphtv.kevinformatics.com/tt1286039
and Battlestar Galactica
(1978) http://graphtv.kevinformatics.com/tt0076984