HBO's smash-hit series Game of Thrones might've been considered a flop 20 years ago, if weighed strictly by classic TV Nielsen ratings metrics. Just compare its numbers to the ones NBC's ER pulled back in 1997. The season three ER premiere, in the fall of that year, drew 42.7 million viewers. Meanwhile, the season six finale of Game of Thrones last June — "The Winds of Winter," the highest-rated episode in the HBO series' existence — got 8.9 million. In '97, that'd be grounds for immediate cancellation.

But that 8.9 million doesn't tell the whole story. HBO also re-ran "The Winds of Winter" throughout the weeks that followed, and made it available to subscribers through its digital platform. Modern content-providers like Amazon, Hulu, and Netflix are often less than forthcoming about how many people actually watch their shows; but if we can believe what HBO itself has announced, then season six of Game of Thrones averaged about 25 million viewers per episode, taking into account all the ways modern TV viewers consume media. And even two decades ago, 25 million would've been impressive.

There's more to "popularity" these days than just eyeballs, too. Each Game of Thrones episode receives a full review/recap in pretty much every major publication that covers popular culture. Several of those outlets follow up the review with essays and listicles throughout the week — dissecting, contextualizing, and in some cases pushing back against what's happening on the show.

HBO's decision not to provide advance screeners of Game of Thrones means that after all the bleary-eyed critics stay up until midnight tapping out insta-reactions, there's still plenty of meat left to gnaw off any given episode's carcass. (By Tuesday or Wednesday, that skeleton is pretty well picked clean. That's when websites start boiling the bones to make soup.)

Because of the intense media attention paid to Game of Thrones, the show's characters, themes, and mythology have permeated the larger culture to a greater degree than just about any other contemporary TV series or movie. Political commentators compare Republicans and Democrats to the Lannisters, Starks, and Targaryens. Phrases like "winter is coming," "the red wedding," "you know nothing, Jon Snow," "mother of dragons," and "a Lannister always pays his debts" have widely understood meanings, which pop up in memes, songs, and other TV dramas and comedies.

The CBS procedural NCIS has been on the air for 14 years, and about 15 million people watch each new episode as it airs — which is nearly double the number who watch Game of Thrones live. But how often do the characters and scenarios of NCIS get parodied on Saturday Night Live, or become analogies for something happening in the real world, or even just pop up in casual workplace conversation?

The second-most popular movie at the U.S. box office in 2017 so far is Guardians of the Galaxy Vol. 2, which is the sequel to another blockbuster, and part of a larger series of mega-grossing films based on Marvel comics. The Guardians movies are genuinely beloved (and rightfully so … they're very entertaining); but again, would anyone argue that Star-Lord, Rocket, and Groot have become as iconic as Tyrion Lannister or Daenerys Targaryen?

By contrast, the biggest hit in cinemas this year is the live-action remake of Beauty and the Beast, which is fairly pervasive in the culture thanks to the 1991 animated version, a staple of family rooms for decades. These days, it's hard to imagine too many new pieces of pop becoming not just a financial success like the original Beauty and the Beast, but also introducing songs and scenes that establish themselves as common reference-points. (Broadway's Hamilton might qualify, though only a fraction of the fans of that show have ever actually seen it performed.)

The media at every level would be thrilled if the public would love a new movie or TV show as much as Beauty and the Beast or Game of Thrones. It's not just producers who want their work to become part of the zeitgeist, but also the people who write about these items. In fact, over the past few years we've sometimes seen a desperate effort to force a new phenomenon, as modestly enjoyed series like Westworld or Mr. Robot spawn their similar assortment of piggybackers: special weekly online features, think-pieces galore, and post-air panel discussions.

Some potential franchises have at times seemed poised to threaten Thrones' dominance. The Walking Dead still draws a healthy number of viewers, though the show is not obsessed-over as much as it used to be. Periodically, a hubbub arises around a project on one of the subscription streaming services — like last summer's Stranger Things on Netflix. Still, Game of Thrones' popularity keeps increasing from year to year; and with only two abbreviated seasons remaining, there's no reason to believe it won't be breaking premium cable viewership records by the time it ends in 2018.

Why this show in particular? It's excellent, for one thing — but then so are Fargo and Better Call Saul, and neither of those dramas have ever reached "phenomenon" status. Game of Thrones appeals to devoted adult fantasy fans, with its sex, violence, and magic — but then so does Starz's Outlander, which thus far has remained more of a cult series.

One intriguing explanation for why Thrones does so well is that it's ideologically ambiguous, seemingly supporting the political leanings of viewers on both the right and the left. Its story has been interpreted as a metaphor for humanity's inaction on global warming (with the massing armies of ice zombies beyond the Wall representing the impending climate change that warring world leaders are failing to address). It's also been alternately slammed and praised for its depictions of race and gender, with viewers on the right getting irritated when episodes seem to lean too progressive, and those same viewers taking a perverse glee when commentators on the left grumble about the preponderance of rape and gore.

Like a lot of action-adventure sagas, Game of Thrones also does well internationally, because even though it's dialogue-heavy, the chatter regularly gives way to bloody battles and mythological monsters. It goes over especially well across Europe, because the show is shot throughout the continent, sports a diverse cast of mostly Europeans, and tells a story that echoes various nations' actual history (minus the dragons and zombies).

Also, those locations — in Northern Ireland and Croatia and Spain — represent an investment in physical spaces that's increasingly rare in both television and movies, where digital effects carry much of the visual load. Game of Thrones relies heavily on digital too, but to complement spectacular real-world sets, many of which are housed in stunning (and sometimes forbidding) landscapes.

In other words: Game of Thrones looks expensive. It's a throwback to the days when resources for something as frivolous as a television production were more plentiful. And as such, it tends to make older viewers in particular nostalgic for a time of conspicuous affluence in the entertainment industry.

More than anything, what makes Game of Thrones so resonant in the 2010s is that the show itself is about the passing of a golden age and the decline of common ideals. The various factions in Westeros are killing each other to reclaim a kingdom that for all practical purposes no longer exists — that has fragmented into regional spheres of influence unlikely to unite behind whomever ultimately sits on the Iron Throne. Audiences may feel a pang as they see themselves reflected on screen each week, roaming further away from an era that seems increasingly like a fairy tale.