Over the years, fans have thrilled again and again to a stark musical cry as the movie begins, the sun rising over an imaginary African landscape: "Na-a-a-nts ingonyama bagithi Baba!" Then the vocal dramatically drops to that breathy, choral-ensemble hum: "Sithi uhm… ingonyama!" From the Zulu language, it means: "Behold a lion, father – yes, a lion." The song then switches to English: "From the day we arrive on the planet/And blinking, step into the sun …" – but, let's face it, they had us at Nants ingonyama bagithi Baba. The classic Disney animated musical The Lion King, directed by Rob Minkoff and Roger Allers, is 20 years old this year — but its popularity and influence are apparently indestructible. It just gets bigger and bigger, enduringly loved on DVD, and now Disney have announced production on The Lion Guard, a TV movie and series inspired by the film and its sequels.

This is the tale of the young lion Simba (Jonathan Taylor Thomas) who was cruelly tricked into thinking that he has killed his own father Mufasa (voiced by the majestic James Earl Jones), and must now rescue his homeland from his evil usurping Uncle Scar (a career-highlight triumph for Jeremy Irons). The film created its own potent legend, its own mythic ecosystem, a movie with its own philosophy of life's circularity, as proclaimed by talking animals. Movie audiences were captivated by this reverent if picturesque vision of "Africa" as a place of Edenic nobility and feudal integrity, a conservative vision of patriarch-worship.

The Lion King was the last Disney picture in the classic vein, perhaps the last Walt Disney movie that the man himself (who died in 1966) might have recognised as something that could have come from his own hand. It was a robustly traditional tale, conceived as a wholesome family musical, with influences from the Bible, Shakespeare and Kipling – and it looked similar to Bambi and The Jungle Book. Digital animation is nowadays supercharged with richness and sophisticated detail; The Lion King's design looks simple in comparison. When the film was revived in London on Imax screens about a decade ago, some of the background looked weirdly inert, like the illustrations of a much-loved children's storybook projected on to the side of a building.

Yet despite or perhaps because of this old-school simplicity, The Lion King continues to triumph. It is powerful and bold. Young Simba (Swahili for "lion") is introduced by his father Mufasa (Swahili for "king") to all his responsibilities as a future monarch. He must respect all creatures "from the crawling ant to the leaping antelope" and when Simba points out that they eat the antelope, Mufasa quietly but firmly explains that when lions die, they become grass "and the antelope eat the grass, and so we are all connected in the Circle of Life". Simba is not so disloyal or disobedient as to point out that that grass does not experience fear and pain, in the way the antelope does. It is a benignly untroubled exposition of the carnivore's natural prerogative and screenwriters might perhaps now feel constrained to acknowledge more explicitly the herbivores' existence. But it is not a bad introduction to the concept that we are all interrelated, and that everything we do has an effect on everything else.

Simba's duplicitous Uncle Scar (a nod, surely, to Shere Khan from The Jungle Book) is plotting to dislodge Mufasa (he is called "Scar" after a facial disfigurement under his left eye – Scar does not get a noble Swahili name). There is a terrifically Shakespearean confrontation between the two brothers and Scar tricks Simba into wandering into a wildebeest stampede. Mufasa saves Simba, but a tragedy ensues – wicked Scar persuades poor little Simba that he is to blame and forces him into exile, where he befriends two goofy new pals: cheeky meerkat Timon (voiced by Nathan Lane) and flatulent warthog Pumbaa (Ernie Sabella). They introduce Simba to the seductive philosophy of "hakuna matata" (it means "no worries") – just as Baloo the bear sang to Mowgli about kicking back with the bare necessities of life. But soon Simba's childhood friend Nala (and now the love of his life) is to return and urge him to face his demons and his destiny.

There are so many tremendous things about this story. Poor Simba actually thinking that he has killed his father is almost unbearable; it is a powerfully real moment of agony. Then there is the terrific musical sequence that captures the adult Simba and Nala falling in love, singing the song Can You Feel The Love Tonight? We get one quite extraordinary moment in which Nala reclines, in an obviously sexual come-hither pose. It is surely the single steamiest instant in Disney history.

The Lion King's fierce mythic potency has had a huge influence on popular culture. This was never more powerfully shown than in 2002, when Michael Jackson showed the world that he was having his own very disturbing "Lion King" moment. While staying in the presidential suite of the Adlon Hotel in Berlin, he held his baby, the then nine-month-old "Blanket" Jackson, over the balcony, apparently "presenting" him to the crowds of press and paparazzi below. Everyone was horrified – and when the explanation for his behaviour dawned, it didn't make anyone less uncomfortable: the King Of Pop was very clearly holding up his young heir, just as Mufasa – in accordance with the invented tradition – would allow his young cub Simba to be ceremonially held up at Pride Rock, for all the animals to bow down to.

The Lion King's success, though not immediate, has grown and grown; the lifetime gross stands at $987,483,777 and climbing. It spawned two moderate direct-to-video sequels, The Lion King II: Simba's Pride, a Romeo-and-Juliet love story between the progeny of Simba and Scar, and the oddity The Lion King 1½ (or The Lion King 3) a collection of sketches and scenes featuring lovable Timon and Pumbaa. But more importantly, in 1997 there was the smash-hit stage version directed by Julie Taymor, which still carries on triumphantly on Broadway, London's West End and around the globe. On Broadway alone, the total current box-office gross is a flabbergasting $1,061,946,670. Everyone in the world, it seems, wants to see The Lion King on stage.

All nature documentaries now have a touch of Lion King about them, in my view. There has always been a bit of anthropomorphisation – now it is very prevalent. For example, a recent film Arctic Tale (2007), narrated by Queen Latifah, featured a polar bear cub and walrus pup called "Nanu" and "Seela", as if this is what the animals' parents had actually called them. Almost all nature documentaries give their animals Lion King-like names and tend to talk about things happening in "Africa" as if it were a big national park without nation states. The documentary March of The Penguins (2005), narrated by Morgan Freeman, is about a very real trek undertaken by Antarctic penguins to their breeding grounds – it is a built-in longer-form narrative and its heart-warming quality has an emotional rhetoric not far from The Lion King.

For me, The Lion King is always very enjoyable, perhaps especially for the old-fashioned pizazz of the musical numbers; Tim Rice's lyrics are terrifically good, especially in the song Be Prepared when Scar promises to pay off his hyena lackeys: "I know it sounds sordid/But you'll be rewarded …" Everything in that song is witty, literate and well-judged and as for the rest of the film … well, they don't make them like that any more.