James Gandolfini: The first, and best, of a new kind of star

James Gandolfini created a monster: like Tokyo after a visit from Godzilla, the pop-cultural landscape was permanently altered by Tony Soprano. Since the troubled wiseguy first went to therapy in 1999, television has unexpectedly become the most vital of creative media. Thinking people spend vast chunks of each week deconstructing the latest episode of their favourite show as if it were 19th-century literature. And thanks to the late, great Gandolfini, the protagonists of the best-loved dramas on the small screen can be bald, or overweight, or bald and overweight, or a dwarf, or Steve Buscemi.

With the Italian-American mob, The Sopranos took a prettified big-screen genre and made it small and ugly. Michael Corleone's organised criminal activities in The Godfather were governed by an old-world honour code; Tony's work was grubby and ignoble. The godfather of suburban New Jersey was a middle-aged lunk, not a svelte young Pacino. So while Hollywood still prizes its heroic Hemsworths and Tatums and Cavills, premium cable now puts a premium on anti-heroic character actors: Michael Chiklis of The Shield, Ian McShane of Deadwood, Peter Dinklage of Game of Thrones.

"Gandolfini's performance as Soprano meant casting directors no longer had to cast guys who were likeable-looking, or even good-looking," says Sarah Bunting, co-founder and East Coast editor of the website Previously.TV. "A 'character actor' used to be some guy you knew from the New York theatre scene who turned up in an episode of Law & Order – someone who looked 'too Irish' to be a star. Now a character actor is the 'real' actor on set. The idea of what is attractive has broadened from simply meaning 'cute' to meaning someone who attracts, interests and compels viewers to keep watching. 'Leading man', meanwhile, has become a somewhat pejorative term."

Not only are TV's leading actors now non-traditional, but so too are the characters they play. In his history of small-screen drama's ongoing golden age, The Revolution Was Televised, Alan Sepinwall writes that The Sopranos dispelled "the notion that a TV series had to have a likeable character at its centre. Why, TV executives had been asking for 50 years, would viewers want to come back week after week to watch a jerk, a crook, or worse? ... Even Sipowicz from NYPD Blue – introduced to viewers as a drunken, profane, sexist, out-of-control bigot... cleaned up his act to the point where it wouldn't have been implausible if he'd been made a candidate for sainthood."

The Sopranos broke that mould. Now, the narrative arc of television's best dramas bends towards injustice. Tony wasn't interested in redemption or self-improvement. In spite of his regular sessions with Dr Melfi, he just got worse. Subsequent protagonists have followed a similar downward trajectory, most spectacularly Breaking Bad's Walter White (Bryan Cranston): a mild-mannered chemistry teacher diagnosed with lung cancer during the pilot episode, who over the course of the following four-and-a-half seasons has become a scheming, murderous meth kingpin.

As the Tony Soprano effect turned character actors into leading men, it also had the opposite effect: turning leading men into character actors. The dashing Jon Hamm was not cast as Man Men's mercurial ad creative Don Draper simply because he was good-looking, but rather because the role demanded good looks. When viewers first encountered the talented, compulsively adulterous Draper, he seemed like another lovable rogue with a past. Yet as the series has progressed, and Hamm's performance has developed and deepened, the glossy exterior has peeled back to reveal a thoroughly rotten core. Like Tony and Walter, Don has become not merely an antihero, but the villain of his own show. Even his protégée, Peggy, recently called him a "monster".

The novel-like narratives of these series have also enriched their peripheral characters, whom the internet has seen fit to turn into cult heroes: Roger Sterling of Mad Men, Saul Goodman of Breaking Bad, or The Wire's fearless, gay, stick-up artist, Omar Little. Character actors have a chance to shine in small parts as well as large.

These phenomena remain almost exclusive to US cable TV channels: HBO became the gold standard for quality original programming with The Sopranos, Deadwood and later Game of Thrones. AMC, its biggest rival, is responsible for Mad Men and Breaking Bad. Showtime has Dexter and Homeland. The most influential network dramas of the past decade, by contrast, were led by conventionally handsome fellows such as Matthew Fox (Lost), Kiefer Sutherland (24) and Rob Lowe (The West Wing), and populated by attractive co-stars – whereas the supporting cast of, say, Game of Thrones, consists largely of British actors with questionable teeth.

Or, at least, the male supporting cast does. Though Game of Thrones is full of funny-looking blokes, its female characters are mostly gorgeous – and frequently naked. Similarly, while Tony Soprano may have made it possible for male protagonists to sink to new depths, the same is not yet true for women. There remains, if you will, a glass floor for female roles. Yes, there have been inklings of what may yet come, from the compelling Carrie Mathison (Claire Danes in Homeland) or Sarah Linden (Mireille Enos in the US remake of The Killing), but both are ultimately admirable characters, despite their glaring personal flaws – and both are played by beautiful women.

"There is still no Antoinette Soprano," Bunting agrees. "It would be nice to see someone on screen who's a little more like most women – who wouldn't have their make-up done properly at a crime scene at 5.30 in the morning. But on American TV everyone is 23 and came straight from pilates to the precinct."

Gandolfini was plucked from relative obscurity to play Tony, but his legacy means such roles are increasingly prized – not least by known character actors, lured from the big screen by the opportunity to spend 12 hours or more in the shoes of a single character. The star of The Sopranos' most direct descendant, organised-crime saga Boardwalk Empire, is Steve Buscemi. Kevin Spacey may just win the first Emmy award for a web-only acting role, for his performance as Machiavellian congressman Frank Underwood in Netflix's series House of Cards.

The most promising new drama of this season is Showtime's Ray Donovan, in which Liev Schreiber, a regular supporting player in movies, takes the lead as a morally ambiguous Hollywood fixer. What was once ground-breaking is now the norm. Which is to say that, though his influence is everywhere, we may never quite see the like of Tony Soprano again.