The greatest comedy of all time in my opinion: "It's a Mad, Mad, Mad World" with the greatest list of comedic actors and actresses ever gathered in one film.
"A New Leaf" (comedy-romance) with Walter Matthau
"Good Neighbor Sam" with Walter Matthau and Jack Lemon
"How to Succeed in Business without Really Trying" with Robert Morse
Dr. Strangelove
M.A.S.H. "Brewster McCloud" "The Life and Times of Judge Roy Bean" "The Sting"
"Arthur" with Dudley Moore
Caddyshack, Groundhog Day,
Animal House, Vacation, "Trading Places"
"Planes, Trains, and Automobiles" with the late John Candy,
"The Gods Must Be Crazy I" and "The Gods Must Be Crazy II"
"Dirty Rotten Scoundrels"
"Ferris Bueller's Day Off" "My Cousin Vinny" "Airplane" "Napolean Dynamite"
"Office Space" "Best In Show"
Great Movie Musicals make for great Lesson Materials for learning English
These are not arranged in a special order, such as "best" or anything like that.
"Oliver!" 1968 http://www.imdb.com/title/tt0063385/
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"My Fair Lady!" 1964
http://www.imdb.com/title/tt0058385/?ref_=fn_al_tt_1
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"The Sound of Music" 1965
http://www.imdb.com/title/tt0059742/
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"The Music Man" 1962 http://www.imdb.com/title/tt0056262/?ref_=fn_al_tt_1
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"West Side Story" 1961 (based upon William Shakespeare's "Romeo and Juliet")
http://www.imdb.com/title/tt0055614/?ref_=fn_al_tt_1
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"Camelot" 1967 http://www.imdb.com/title/tt0061439/?ref_=fn_al_tt_2
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"State Fair" 1962 http://www.imdb.com/title/tt0056526/?ref_=fn_al_tt_1
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"The King and I" 1956 http://www.imdb.com/title/tt0049408/?ref_=fn_al_tt_1
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"Mary Poppins" 1964 http://www.imdb.com/title/tt0058331/?ref_=fn_al_tt_1
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I'd recommend: Ted, 21 Jump Street, 22 Jump Street, and Mrs. Brown's Boys.
They're silly but really hilarious.