Quincy ME had a very long run (8 seasons) and doesn't really qualify for this thread. The thread is "brilliant TV series that were cancelled." All TV series eventually get cancelled, even Gunsmoke after 20 years or so. I think the OP's intention was to confine the thread to brilliant shows that were overlooked and cancelled after a very short run.
If you want to talk Jack Klugman, he did the very best acting of his long and distinguished career in 4 Twilight Zone episodes in the early 1960s in which he played highly emotional and temperamental characters. The Twilight Zone may have been the most brilliant TV show of all time, but it ran for 5 seasons and it doesn't really qualify for this thread either.