Die Hard is the godfather of an entire genre of movies, from Con Air (Die Hard in a plane) to Home Alone (Die Hard in a house with a kid as John) to Paul Blart: Mall Cop (Die Hard in a laboured metaphor for the toilet of the soul). With a fistful of sequels and countless knock-offs in its wake, Die Hard is still the best of the lot by a long shot.
So, what makes it work?
So much of the fun of Die Hard is in its simplicity, one cowboy against impossible odds in a confined space. With everyone inside the building desperately unable to get out and everyone outside desperately unable to get in, the film feels confined and claustrophobic. The seemingly endless limitations put on John make each and every success that much more triumphant.
Unfortunately, Hollywood is a slave to the More Is More Aesthetic of Filmmaking and the knockoffs and sequels frequently eschew the cold efficiency of the original for greater thrills.
It's the difference between Pitch Black (tight, terrifying) and The Chronicles of Riddick (so stupefyingly expansive, it's stupid). It's the difference between Raiders (every punch has impact) and Kingdom (the less said about the refrigerator, the better).
Exceptions to this rule, rare though they are, do exist. For example, Aliens expertly takes the rules of the first film, jams them into the More Is More machine and the results are thrilling.
Love Of Procedure
Die Hard is uncommonly obsessed with procedure. Despite the ever-growing number of ingredients thrown into the blender, McTiernan regularly breaks from the action to show technical processes. Whether it's the terrorists securing their missile launcher to the floor or John checking that there's ammo in the pistol that he just stole from a baddie, these little touches bring a sense of grounding to the patently absurd spectacle. Even if it's just at a subconscious level, these small touches contribute to the sense that the world (and, by extension, the danger) is real.
Heroes are all well and good, but audiences need a villain to latch onto. Antagonists act, protagonists react. The reaction can only be as interesting as the action.
For a perfect example of how an impotent villain makes for an impotent hero, compare The Dark Knight to The Dark Knight Rises. In the former, The Joker single-handedly conquers every crime syndicate in Gotham, gleefully destroying the cash spoils of his victory. He's a master of Batman's collective enemies and The Joker treats this victory as a minor trifle.
Batman must up his game to match the threat. In Rises, Bane shows his dominance by blowing up a football field. His ambitions are small and arbitrary in Bruce's world. Batman has less to react to and the film suffers for it.
Hans Gruber is as huge as a villain can be. He's so far ahead of the game that he's got the entire FBI in his pocket and they don't even know it. He's charismatic, funny and merciless. He could have killed any of the hostages to prove he was serious, but he goes for the highest ranking member of the party.
With so much to react to, John McClane is always on the move and we, as the audience, are struggling to keep up with him.
Die Hard's primary stock in trade is layers. The scene structure is essentially an alternation between "add chaos", "John adapts to chaos", "add chaos", "John adapts to chaos". The ability to walk this tight rope is one of the miracles of Die Hard. When films continually compound chaos, it's easy for the story to buckle under the weight of it all (again, see Dark Knight and Dark Knight Rises for a perfect contrast of chaos logically compounded and chaos chaotically compounded).
One key scene that keeps the chaos from landing on the silly side of the equation is when John is picking glass from his feet in the bathroom. He's been battered, beaten, shot at, and his head was used repeatedly to smash dry wall and steel girders.
And he admits, his file might be closed soon. He doesn't want to give up. He's just running out of ideas and options and that reality is setting in. The moment of quiet gives weight to the chaos.
What Doesn't Work
All said, there are parts of the film that simply don't play. A police lieutenant who is so pathologically stupid he seems programmed to do the exact opposite of what logic would mandate diffuses the tension outside of the building.
A news reporter so anxious to get a scoop that he would broadcast personal information about a family in a desperate hostage situation suggests that this film takes place in an America where civilians have no legal recourse against psychotic newscasters.
A first responder who threatens legal action against someone making an emergency call regarding a terrorist threat on an emergency line is necessary to keep the story moving. But, it sure does feel like stretch.
That said, the elements that don't work simply don't matter. This is a story about a rough and tough cop kicking terrorist ass in a high-rise so he can be with his family again. Movies like this don't exist for the logical sinew that connects the narrative bones. They exist so we can watch some bones get shattered. Die Hard maintains constant momentum without sacrificing pathos, a feat incredibly rare in the action genre.
Maybe that's the reason that every other film is described as "Die Hard in/on a..." and this one is simply "Die Hard".