Announced every ten years. Latest list released today...
Top 10
1. Vertigo (1958) Hitchcock
2. Citizen Kane (1941) Welles
3. Tokyo Story (1953) Ozu
4. The Rules of the Game (1939) Renoir
5. Sunrise (1927) Murnau
6. 2001 (1968) Kubrick
7. The Searchers (1956) Ford
8. Man with a Movie Camera (1939) Vertov
9. The Passion of Joan Arc (1927) Dreyer
10. 8 1/2 (1963) Fellini
Rounding out the list...
http://www.bfi.org.uk/news/50-greatest-films-all-time