I was, at the time, deeply disappointed by the cancellation of DARK SHADOWS (1991), so much so that I pretty much boycotted watching any new network TV series fo years.
I'll second the loss of BOSS (2011), a very enjoyable political melodrama that I enjoyed even more than the early seasons of HOUSE OF CARDS (which came along right after). Kelsey Grammer hasn't had much post-FRASIER success with series. I also enjoyed his sitcom BACK TO YOU (2007), but it didn't last a full season.
From 2007, I also liked SAMANTHA WHO? with Christina Applegate, but that one only lasted 2 seasons. After that, I pretty much stopped watching sitcoms; my track record of picking them was even worse than prematurely cancelled soaps.