Die Hard is the finest action movie ever made. The matter isn't even up for debate in my eyes as it was the footprint that has spawned hundreds of inspired action flicks since, that breathed fresh impetus into the genre, reviving it and keeping it current for a new generation. Plus, it was the film that gave us Bruce Willis the film-star rather than simply that cocky, likeable chap from Moonlighting.

The aspect of the film that marked it out from so many other, tired action movies at the time was that we were presented with a flawed everyman. Armed with a handgun and his own ingenuity, John McClane is simply the wrong guy, in the wrong place at the wrong time. But hell, who else is going to save the day from the terrorists?

The plot of Die Hard seems at first glance to be alarmingly simple. Terrorists ('Who said we were terrorists?') have taken over a huge corporate building, interrupting the office Christmas party. New York Policeman John McClane is visiting his wife for the holidays so gets wrapped up in the chaos and takes it upon himself to save the day. With nods to almost any Western you've ever watched, this is a modern day take on the likes of Shane where the outsider must save a bunch of people he has little time for because it's just the right thing to do.

Yet while this lone-gunman-takes-on-the-posse storyline is easily recognised by any film-goer, what's less familiar, at least at the time it was released, is the way the film goes about things.

Take McClane for starters. While it's obvious that he is frequently out of his depth he quips his way through the film with such ease that his charm becomes an integral part of the film. This isn't just about decapitating a bunch of evil terrorist chaps; this is also about one man's survival against all odds.

The terrorists themselves are also as far removed from your typical bad guys as it's possible to be. Their leader, Hans Gruber, is a well-dressed, well-spoken, educated man who wouldn't look out of place managing a bank. The outstanding performance from Alan Rickman matches Willis toe for toe, with one of the film's highlights being their first encounter on the rooftop of Nakatomi Plaza. Gruber's switch to Bill Clay is a master-stroke and the way you're at first led to believe McClane has fallen for it is well executed. Other little moments among the terrorists – the passing around of candy just before the big guns weigh in to smoke them out chief among them – lend the group a believability that other action films regularly fail to imbue its bad guys with.

As for those big guns, the film brilliantly turns the notion of the good guys being any kop at what they do on its head as first the Police force and then the FBI are to a man exposed as being utterly inept. All that is except for one man: Al. Providing McClane with a friendly voice on the end of the line, a chink of light at the end of the tunnel, Al is the film's primary love story – the love between a couple of friends who barely know each other and yet pull each other through this most horrendous of nights.

I'm not kidding here, I see Al and John's relationship as closer than the one he has with his own wife and I'm waiting for the spin-off romance flick. Okay, so maybe I am kidding about the last bit but Al does have a massive role to play throughout the film, not least offing huge German Karl in the movie's final moments – the one part of Die Hard that has never worked for me, truth be told. It feels tagged on at the end just to give Al his chance for redemption and it's off kilter with the rest of the movie in my view just for the sake of some good old fashioned cheese.

Throw in a couple of subplots involving McClane's chauffeur, employee Ellis who thinks he can best the terrorists ('Hans, Bubi. I'm your white knight!') and a reporter who just won't give up on a story and you have a packed narrative to match the packed action. And what action. FBI helicopters being blown up, bombs being detonated down elevator shafts, hand-to-hand face-offs that never outstay their welcome (take note Seagal), guns a-plenty and a fallen terrorist in a Santa costume ('Now I have a machine gun, Ho Ho Ho'). Die Hard has the lot.

A film that's eminently quotable ('Fists with your toes', 'Alas your Mr Takagi did not see it that way so he won't be joining us for the rest of his life', 'Shoot the glass'), that features so many easily recognisable action scenes it's hard to keep count and has performances that wouldn't be out of place in a drama, Die Hard remains after 21 years the most intelligent, exciting, funny and downright brilliant action film ever made.

We have yet to see its like again, although as I'll cover shortly, the series has tried to recapture the magic of this first outing.