re: Was 1939 the greatest year for new movie releases in film history?

Good year. The Rules of the Game is one of those foreign language classics that I still haven't seen, routinely mentioned up their with Citizen Kane, Vertigo, The Godfather etc.

1974 was a good one:

The Godfather II
Chinatown
The Conversation
A Woman Under the Influence
Young Frankenstein
Bring Me the Head of Alfredo Garcia
The Texas Chainsaw Massacre
Blazing Saddles
Thunderbolt and Lightfoot
Murder on the Orient Express
Death Wish
The Sugarland Express
Dark Star
The Phantom of Liberty
The Parallax View
Alice Doesn't Live Here Anymore

Big year for Francis Ford Coppola and Mel Brooks. Carpenter, Scorsese, Cassavetes, Bunuel, Peckinpah, Carpenter, Spielberg, Lumet and De Palma came out with good ones that year too.

Found a couple of articles with 1939 and 1974 both included in their top years. 82 and 99 also mentioned in both.

The Greatest Years in Movie History
What was the Best Year in Movie History

That first one talks about 1982 having the best summer ever:
Blade Runner - The Thing - E. T. - The Road Warrior (American release) - Poltergeist - Conan the Barbarian - Fast Times at Ridgemont High - Tron - Star Trek II: The Wrath of Khan - The Secret of NIMH.