Each decade seems to have a film indelibly tied to it. In most of these movies an attempt is made to show modern people of the time in their natural habitat. These accidental period pieces are the prodigies of the prevailing pop culture.
1950s - Rebel Without A Cause. I think I heard the term Daddy'O in this one. If not, it was certainly implied.
1960s - Doctor Strangelove - Forget the Beach Blanket Bingo crowd. This Kubrick masterpiece captures the mindset of the decade.
1970s - Saturday Night Fever - The political impetus of the 60s fizzles out and this is what we have in terms of residue. Sucked. But so did the 70s.
1980s - We have a tie. Desperately Seeking Susan and Wall Street. Respectively, Those who didn't give a shit and the reason why they didn't give a shit. (The brick Michael Douglas talked into is worth a good laugh today. )
1990s - Clueless - Seems like all the other movies of the day were period films. Once again watch the cell phones and you'll have a clue about this 1995 release,
2000s - So far it seems to be all cartoons or comic book hero fare. Take your pick from one of the Bourne films and their ilk. Gadgets vs. terrorists seems to be the theme so far this century.