The British Film Institute (BFI) is an excellent source of information about films from all eras and countries.
Every decade, they conduct a poll on the top films of all time. Here’s a link to their latest poll (2012) which named Vertigo as the greatest film of all time.
They also have lists on specific people, countries, and subjects. I recommend the lists of 10 great South Korean action films and 10 great silent romances. There are many other fine lists to pick from.