In the US, they have a "National Film Registry" administered by the Library of Congress through its National Film Preservation Board. It is described as "a list of films deemed "culturally, historically or aesthetically significant" that are earmarked for preservation by the Library of Congress. These films are not selected as the 'best' American films of all time, but rather as works of enduring importance to American culture. They reflect who we are as a people and as a nation." The public nominate titles (which should've rbeen released at least 10 years ago) for inclusion into the list each year, and the Libraian of Congress names 25 films as inductees. The first registry was named in 1990.
http://www.loc.gov/programs/national-film-preservation-boardIt will be a great idea to adopt a similar project for our own films. As for me, the following titles comes to mind (I've limited my choices to the ones I've seen, and those which were at least 20 years old):
Anak Dalita
Badjao
Biyaya Ng Lupa
Sisa
Confradia
Noli Me Tangere
Patayin Sa Sindak Si Barbara
Ibulong Mo Sa Hangin
Ang Pinakamagandang Hayop Sa Balat Ng Lupa
Tinimbang Ka Ngunit Kulang
Maynila Sa Mga Kuko Ng Liwanag
Banaue
Tatlong Taong Walang Diyos
Pagputi ng Uwak, Pag-itim ng Tagak
Itim
Insiang
Ganito Sila Noon, Paano Kayo Ngayon?
Burlesk Queen
Kung Mangarap Ka’t Magising
Ina Ka Ng Anak Mo
Nunal Sa Tubig
Ang Panday
City After Dark
Aguila
Kisapmata
Temptation Island
Salome
Katorse
PS I Love You
Gaano Kadalas Ang Minsan?
Himala
Oro Plata Mata
Moral
Soltero
Karnal
Bagets
Working Girls
Saan Darating Ang Umaga?
Shake, Rattle, & Roll
Sister Stella L
Scorpio Nights
Private Show
Takaw Tukso
Itanong Mo Sa Buwan
Tiyanak
Pahiram ng Isang Umaga
Bilangin Ang Bituin Sa Langit
Gumapang Ka Sa Lusak
Kahit Konting Pagtingin
Hihintayin Kita Sa Langit
Jose Rizal
Sana Maulit Muli