Well, Star Wars is like that too, from a cinema-history point of view. The conventional wisdom, of which we're going to be hearing a lot now that the trilogy is coming out on DVD, is that Star Wars (along with Jaws) brought the new Golden Age of Cinema to a close and ushered in a new, horrible era of blockbusterism. This article pretty much sums up the conventional wisdom: George Lucas betrayed himself and the art of cinema and condemned us all to bland, disposable entertainment. Leaving aside the point that the '70s produced plenty of bland, disposable entertainment before Star Wars (the big hits tended to be stupid disaster movies, exploitation shockers, and non-Deliverance Burt Reynolds movies), a lot of these critiques ignore the obvious question: why did Star Wars become such a phenomenon? -- and the obvious answer: because it was exactly what audiences were looking for at the time. And the reason the success of Star Wars had such an impact is that it demonstrated something about the tastes of the audience, just as the political success of Reagan would demonstrate something about the opinions of the electorate.
By the '70s, because of the collapse of the studio system, the rise of the New American Cinema, and new trends in movie criticism, there was a tendency to believe that the audience had developed a new sophistication and that the old formulas -- of heroes and happy endings -- were no longer needed. Even aging filmmakers like Alfred Hitchcock were of this opinion; here's Hitchcock being interviewed by Francois Truffaut in 1972:
TRUFFAUT: Do you think the old rules still apply, namely that an appealing main character and a happy ending are still valid?
HITCHCOCK: No. The public has developed. There's no more need for the final kiss.
Hollywood studios in the '70s tended to make movies that assumed that the audience had developed, and that therefore movies with a gritty look, moral ambiguity and dark endings would be more to the public's taste than old-fashioned stories with happy endings. What Star Wars demonstrated conclusively is that the public hadn't "developed" at all, hadn't lost its taste for good guys and happy endings and old-fashioned studio magic (Lucas made Star Wars in England, which at the time offered far better studio technicians and special effects than America; and part of his stated reason for doing so was to see if he could make a movie with the look of an old studio film, rather than the on-location look of most '70s movies). Give the public a well-made, morally unambiguous adventure with appealing characters, and they'd flock to it just as they had in the past; the problem with the old-fashioned movies of the '60s wasn't that the public didn't want heroes and happy endings, but that those movies were badly made. In other words, I don't think Star Wars changed the public; it pointed up what was always true, but which the studios had forgotten: tastes never change that much, and the idea that "the audience has developed" was a myth. Like Reagan, it didn't change things so much as it revealed how little things had changed.
You could argue that it was Jaws, two years earlier, that ushered in the era of the blockbuster and revealed how little the public had changed, or perhaps it was Rocky, the year before. But Jaws and Rocky both had the gritty look of the typical '70s movie: the former looked like a bigger-budget version of the TV shows its company, Universal, was producing at the same time, while the latter was, like many '70s movies, a story about losers looking for a break, the only difference being that the break actually comes. They weren't a template for future success, and attempts to mimic Jaws didn't do very well, just as attempts to mimic The Godfather didn't do very well. Star Wars, on the other hand, did provide a template for future success, because it set down some rules that studios could follow in looking for a hit: have clear good guys and bad guys, go for an old-fashioned studio look instead of the washed-out look and inaudible dialogue of a Robert Altman movie; try to appeal to younger and older viewers alike. These were, again, not new rules; they were old Hollywood rules whose effectiveness the studios were rediscovering.
Star Wars also provided a model for how the studios could distinguish movies from television. Ever since television took off, the history of cinema is basically the history of how the studios tried to distinguish their products from television shows, how they tried to offer something that television couldn't. In the '50s and '60s, the solution was to have wider screens, longer movies, more lavish production values. That dried up in the late '60s, and the studios turned instead to loading up their movies with stuff that TV couldn't do: gritty realism, realistic violence, shocking language, nudity. By the mid-'70s, that wasn't working so well; television couldn't do nudity or swearing (HBO would come along a few years later to fill that void), but TV dramas were getting grittier and tougher, and it was increasingly hard to tell a Universal movie from a Universal TV show, given that they were shot on the same streets by the same technicians and had the same kind of dialogue and stories. Star Wars, with its English studio technology and its special effects designed to delight rather than horrify, provided the answer of how to make movies different from television: make them better-looking, glossier, and with better special effects than TV shows. Critics bemoan the movies' post-1977 dependence on special effects, and sometimes even I bemoan it, but the reason for it is obvious: to compete with television, movies have to be able to show things that TV cannot. Wondrous and fantastical special effects are just about the only thing left in that department. And Star Wars clued the studios in to the fact that they could make their movies more successful not by making them grittier, but by going in the opposite direction and making them look better. This, I think, set off something of a technical revolution in Hollywood; studio technicians and technology in Hollywood soon shot far ahead of where they had been in the '60s and '70s.
One more thing to note about Star Wars is that even if you consider the '70s a golden age of cinema, it's hard to argue that Star Wars ended it. 1977 was a pretty bad year for movies (and 1975, the year of Jaws, was perhaps even worse). I'm not a big fan of Star Wars -- I think the Indiana Jones movies, especially the first two, are Lucas's best creations -- and yet I would argue that it should have won the Best Picture Academy Award for that year; the winner, Annie Hall, is even more superficial than Star Wars (I'd rather hear about how the Force will be with me than about how it's tough for Woody Allen to sustain a relationship), and the other three nominees were pretty dismal: The Goodbye Girl (a two-hour Neil Simonism), The Turning Point (a ballet bitchfest), and Julia (Lillian Hellman whitewashes her past and Jane Fonda puts it all up there onscreen). It's not saying much, but Star Wars is the cream of that crop. (You can also make an Oscar argument for two movies that weren't nominated, Close Encounters of the Third Kind and 3 Women. I'd still pick Star Wars, I think, having no great love for Spielberg in his "New Age religion" mode or Robert Altman trying to mimic a movie, Persona, that I thought was overrated in the first place.) Star Wars didn't burst into a cinema golden age; it burst into an age of slick, bland, New York-centred entertainments that represented the Hollywood studios' idea of sophistication. Whatever risks were being taken in the late '60s and early '70s, it was pretty much over by 1975, a victim of the self-destruction of some New American Cinema filmmakers, and of the simple fact that a lot of the "classic" movies of that era weren't very big with the public. The studios had, in essence, given young filmmakers a lot of freedom because they, the executives, had no idea what the public wanted. When the young filmmakers proved that most of them had no idea either, they started to fade away; all Star Wars did was allow the executives finally to figure out what the public did want. Honestly, though, I'd say that the post-Star Wars blockbusters are far more watchable than most of the big hits of the '70s. I'd rather sit through Raiders of the Lost Ark or Die Hard than through Earthquake or The Poseidon Adventure or Smokey and the Bandit, which was released on the same day as Star Wars. Maybe there's a Reagan analogy there, too: you can say the Reagan years were bad, but does that mean you have to be nostalgic for Nixon or Carter?