The 50s are a decade from which I haven't seen too many films (the only one I know even less from are the 40s), and that's a reason why I chose the 90s for my previous post. "> 

Some personal favs on your list, and many I haven't seen. "> 
But also some that I would have considered when I was younger, but which "disappointed" at the most recent re-watches (On the Waterfront, The Seven Samurai, Rear Window,...). By that I mean they just weren't as great as I remembered (I haven't lost my appreciation of them though, and who knows, maybe they'll be included after another rewatch "> ). 
I hope this won't happen with many of the one's I'll list below, and as time goes by only more will be added. "> 

1950 
Rashômon (Akira Kurosawa / Japan) 
Sunset Blvd. (Billy Wilder / USA) 

1951 
Bakushû Early Summer (Yasujiro Ozu / Japan) 
Susana (Luis Bunuel / Mexico) 

1952 
Le plaisir House of Pleasure (Max Ophüls / France) 
Limelight (Charles Chaplin / USA) 
Saikaku ichidai onna The Life of Oharu (Kenji Mizoguchi / Japan) 
Umberto D. (Vittorio De Sica / Italy) 

1953 
Pünktchen und Anton Punktchen and Anton (Thomas Engel / West Germany, Austria) 

1954 
Magnificent Obsession (Douglas Sirk / USA) 

1955 
Dolina Miru Seargent Jim (France Stiglic / Yugoslavia) 
Ordet The Word (Carl Theodor Dreyer / Denmark) 
Pather Panchali Song of the Road (Satyajit Ray / India) 
Rebel Without a Cause (Nicholas Ray / USA) 
The Night of the Hunter (Charles Laughton / USA) 
Ukigumo Floating Clouds (Mikio Naruse / Japan) 

1956 
Soshun Early Spring (Yasujiro Ozu / Japan) 

1957 
Aparajito The Unvanquished (Satyajit Ray / India) 
Kumonosu jô Throne of Blood (Akira Kurosawa / Japan) 
Letjat zhuravli The Cranes are flying (Mikheil Kalatozishvili / Soviet Union) 
Paths of Glory (Stanley Kubrick / USA) 
The Incredible Shrinking Man (Jack Arnold / USA) 
Yorokobi mo kanashimi mo ikutoshitsuki Years of Joy and Sorrow (Keisuke Kinoshita / Japan) 

1958 
Cat on a Hot Tin Roof (Richard Brooks / USA) 
Dokufu Takahashi oden A wicked Woman (Nobuo Nakagawa / Japan) 
Popiól i diament Ashes and Diamonds (Andrzej Wajda / Poland) 
The Fly (Kurt Neumann / USA) 
Vertigo (Alfred Hitchcock / USA) 

1959 
Anatomy of a Murder (Otto Preminger / USA) 
Ballada o soldate Ballad of a Soldier (Grigori Chukhraj / Soviet Union) 
Ben-Hur (Wiliam Wyler / USA) 
Les quatre cents coups The 400 Blows (Francois Truffaut / France) 
North by Northwest (Alfred Hitchcock / USA) 
Rio Bravo (Howard Hawks / USA) 

by country 

USA: 14 
Japan: 8 
France: 2 
India: 2 
Soviet Union: 2 
Denmark: 1 
Italy: 1 
Mexico: 1 
Poland: 1 
West Germany: 1 
Yugoslavia: 1 

________ 

Total: 34 

*added Luis Bunuel's Susana (1951). A film for the ages.