One Flew Over The Cuckoo’s Nest (1975) - Jack Nicholson’s troublemaking R.P. McMurphy shows some mental patients how to really get crazy in this one of a kind film from Milos Forman that swept all five major Oscars (Best Actor, Actress, Director, Screenplay and Picture).
The Sting (1973) - A handsome, jaunty crime caper that stars Paul Newman and Robert Redford as two 1930s Chicago con-men looking to get even with a vindictive mob boss, all to an unbeatable ragtime score. The Sting reigned as Best Picture between the two Godfather flicks.
Taxi Driver (1976) – Martin Scorsese’s stunning, discordant drama with a young Robert DeNiro’s iconic portrayal of a lonely cabbie driven to terrible violence in NYC, retains its disturbing edge even today.
Texas Chainsaw Massacre (1972)- This phenomenal slasher–film progenitor shocked and frightened a generation with its brutal, low budget, yet authentic violence and creepy family of flesh-eating (yet non-dead) killers.
Also great and influential, in no particular order, are Alien (1979), A Clockwork Orange (1971), Saturday Night Fever (1977), The Mack (1973), Apocalypse Now (1979), and Marathon Man (1976). And probably about ten other films, whose lack of visibility in this article many of you will protest angrily. Blame the 70s for being so great. You are allowed to make your own list, after all.