My picks, from what I've seen:
10. Scarface (1983)
9. The Godfather III (1990)
8. Chinatown (1974)
7. The Irishman (2019)
6. The Departed (2006)
5. White Heat (1949)
4. GoodFellas (1990)
3. Casino (1995)
2. Godfather Part I (1972)
1. Godfather Part II (1974)
There are plenty I still need to see, and here is a good list from Newsweek.