Another commented: "He let Rachel be a hat... Rest Easy sir."
Others highlighted his wider body of work, including several roles in Law & Order and a little known film Wher's Poppa.
The actor won a Tony Award for Best Actor for his performance as Roy Cohn in Angels in America in 1993.
He also played the handsome union organiser, Reuben Warshowsky, who helps convince Sally Field's Norma Rae to unionise her cotton mill.
Field won a Best Actress Oscar for Norma Rae.
For younger audiences he was known as Rachel Green's father in Friends.
He also had a recurring role in The Sopranos as Dr Lior Plepler and appeared in the movie Garden State.
The pair had been married since 1983.
He was previously married to actress Linda Lavin, who starred in the TV show Alice, from 1969 until 1981.