Aficionados will be shrugging their shoulders, figuratively if not literally, but the uninitiated might find such characters a little odd. Some people can't suspend their disbelief or find superheroes uninteresting or silly. Fair enough (but their loss).

Superhero fandom seems to have gone from geeky pastime to mainstream movie franchise material, even progressing into a serious field of academic study. Traditionalists might wince at that last part with mutterings about the juvenilisation of culture but is exploring superheroes any different from taking any other folklore or mythology seriously?

There has always been something faintly ludicrous about a lot of superheroes with their costumes and powers and bizarre enemies (one of Superman's foes is Mister Mxyzptlk: in most stories the only way our hero can banish the annoying trickster to his own dimension temporarily is to trick him to say or spell his own name backwards. I mean, really?).

For a long time it seemed like superhero comics were mostly for geeky - and mostly young - devotees, whether the stories were serious or silly or somewhere in between. Whether it was pure escapism or vicarious wish fulfilment - vanquishing foes and triumphing - they struck a chord.

Despite Dr Fredric Wertham's fearmongering, often misleading or downright inaccurate 1954 comic-book "exposé" Seduction of the Innocent - that linked comics with juvenile delinquency and argued, among other things, that Bruce Wayne and his "ward" Dick Grayson were - gasp! - in a homosexual relationship, it's hard to see what the fuss was about. Parents should have been glad their kids were reading at all. Nowadays, superhero studies - covering comics, movies, TV, streaming and more - could lead to a PhD.

Sometimes those involved in creating screen superheroes acknowledge the ludicrous elements and go all out for comedy - remember the brief but intense Batman craze of the 1960s that captivated adults as well as kids? That TV series amped up the camp, with its earworm theme tune, deadpan narration, catchphrases (Robin's "Holy [whatever] Batman!", et cetera), hammy villains and stoic heroes. Poor Adam West (Bruce Wayne/Batman) and Burt Ward (Dick Grayson/Robin) got so indelibly identified with their roles that they could never escape the characters' shadows.

The next big attempt to bring superheroes to the mainstream audience beyond kids was the big-budget 1978 Superman movie starring Christopher Reeve as the Man of Steel (so-called, though his strength and power seemed to go far beyond that and the old 1950s TV series description of him as "more powerful than a locomotive/faster than a speeding bullet/able to leap tall buildings in a single bound". This Superman could fly into outer space and even make the Earth, and time, turn backwards.

Under director Richard Donner, the first film managed to tread the fine line between spoofy and serious. It had a sense of humour as well as providing plenty of action while honouring the history and heritage of the man from Krypton. (Reeve made Clark Kent very different, so it seemed plausible Superman could go undetected in just a pair of specs and a suit).

The Christ-like element, with Jor-El (a very well paid Marlon Brando) sending his only son Kal-El (guess who?) to Earth to help mankind, was very apparent here.

Three sequels followed: the second was taken over by Richard Lester who favoured a more overtly comedic approach. The last two aren't worth mentioning. Superman has been revived, of course, but in some ways he's a dull hero. Given his only weakness is Kryptonite (of which there seems to be quite a bit floating around) and he's a goody-two-shoes, what little depth is in him was mined in the Reeve movies (though even when he voluntarily gave up his virginity, uh, power, he was able to get it back again, so no biggie).

TV had a shortlived 1970s Spider-Man series and a more successful Incredible Hulk show. Hulk is another dull movie character - OK, he's big and green and strong and mad, so what? He works better in an ensemble.

But it wasn't until more recently that superheroes really became huge. New technology meant just about anything was possible and Hollywood's increasing reliance on franchises made these pre-existing characters eminently exploitable. And now it's hard to keep up with them all. From identification to pure escapism, there's a superhero for every desire.

DC tends to be more Serious than Marvel - DC's vigilante Batman has been portrayed in movies far more darkly on the whole than, say, Marvel's Spider-Man, though the latter's adolescent angst is probably more relatable than Batman's neuroses. But the notorious nipple suits in the Joel Schumacher Caped Crusader movies might have made Dr Werther's antennae twitch. Marvel's more inclined to balance humour and heart - you can feel a sense of loss at the end of Avengers: Endgame.

Not every superhero triumphs. Green Lantern and the Fantastic Four didn't work and Eternals was a rare Marvel film that was played Very Serious: it was dull and not a great financial success. The characters and their stories just didn't click with audiences. Why? If studios knew that, there would be no flops.

Getting back to Guardians of the Galaxy: this wasn't one of the better known Marvel comics but it's proven its worth and the trailer for the new instalment suggests it's got the lot - action, adventure, and emotion. There's a big focus on friendship and the family you make for yourself - and that resonates with many.

Guardians of the Galaxy Vol. 3 is now in cinemas.