1970s - tie between Raging Bull and The Deer Hunter
1980s - Angel Heart and GoodFellas
1990s - Cape Fear, Ronin,Casino and Heat
2000s - The Score, 15 Minutes
1970's - Taxi Driver
1980's - Raging Bull
1990's - Heat, Casino and Goodfellas are the obvious choices, but I'll go with Cape Fear just to be different
2000's - The Good Shepherd
2010's - Machete
IMO, rightfully mentioned as one of the greatest films ever made. Placed fourth on the AFI Top 100 after Citizen Kane, The Godfather and Casablanca, and dozens of other top ten all-time lists.
And the best reason why it's an all-time great film: it was snubbed for best picture by some so-so Oscar bait that happened to be directed by Robert Redford and starring Mary Tyler Moore (both of whom the Academy has a huge hard-on for). No better indicator of a great movie than the Oscars whiffing on it.