Every year can be defined by a single movie.
No, not all. 1984, 1987, 1994, 1999, 2001, 2002 are all easy examples of years that can't be quantified by a single film. You can call out a big film from one of those years but like now with EG and Joker I could easily name one or more other films that were just as impactful and "defining."
Oh, this might be fun!
Let's see what movies I can remember from the 70's onward...
1970: Probably Love Story (top of the Box Office), I think that movie was all everybody could talk about that year... But I guess something like MASH probably has had a more lasting impact.
1971: Tough year... there's plenty of widely acclaimed classics like French Connection, Dirty Harry, Clockwork Orange, Fiddler on the Roof (top of the Box Office) and Last Picture Show...
1972: Godfather. Nothing else to say about that. (of course there's also Last Tango in Paris and Deliverance)
1973: The Exorcist.
1974: Chinatown and Godfather II are hard to beat...
1975: Jaws.
1976: Taxi Driver and Rocky. Probably in inverse order.
1977: Star Wars.
1978: Grease. But I'd say The Deer Hunter had a more lasting and (obviously) deeper impact.
1979: Tough one, because it has two of my all-time favourite movies: Alien and Apocalypse Now, and both are considered classics that have influenced film-makers for decades. But I'd guess The China Syndrome and Kramer vs. Kramer ruled that year.
1980: The Empire Strikes Back, but honorable mention to Raging Bull and The Shining for lasting impact.
1981: Raiders of the Lost Ark.
1982: E.T. (of course, we all know Blade Runner and The Thing went on to influence movie-making for ever and cult status)
1983: Return of the Jedi. But Flashdance and The Big Chill were really big.
1984: Got to be Ghostbusters. And I don't even think it's such a great movie...
1985: Back to the Future.
1986: Platoon. Another one I don't think is all that great.
1987: Probably Fatal Attraction or Wall Street. Or Dirty Dancing
1988: Die Hard. But I would also mention The Accused, I remember that movie sparked a huge discussion.
1989: I'd say Batman and When Harry met Sally, but I think that Do the Right Thing and The Little Mermaid had a more lasting impact.
Anybody want to do the 90's and 00's?