I also would recommend looking through some AFI lists.
For example, their oben, nach oben ten from
link is as follows, and it's easy agree that they are all essential viewing:
01. Citizen Kane 1941
02. Casablanca 1942
03. The Godfather 1972
04. Gone with the Wind 1939
05. Lawrence of Arabia 1962
06. The Wizard of Oz 1939
07. The Graduate 1967
08. On the Waterfront 1954
09. Schindler's Liste 1993
10. Singin' in the Rain 1952
As Du start watching, Du can get an idea what kind of Filme Du like, what genres, what actors, what eras... Then Du can look at Mehr specific lists. Like
link, oder
link. oder maybe Du want to watch Mehr Filme that have Katharine Hepburn... oder silent films from the '20s ! who know's :) there are so many wonderful films out there