It's simple: terrorists have taken over a high rise in the middle of a Christmas party, taken all the people inside hostage, and the only man who can stop them is John McClane, a cop who happened to avoid their sweep. Oh, and his estranged wife is among the hostages. However, Die Hard
does so much more with this that it's obvious why it's a classic.
The suspense in this film is amazing; it's obvious the terrorists put a lot of planning into the takeover of Nakatomi Plaza, but they always manage to top themselves. Police called in and surrounded the building? Not only have they prepared for it, it's an important part of the plan. Even when McClane has taken out half of them, they stick to their plan, and come this
close to succeeding. However, it's never quite so prepared that you think they have ESP or something; they just have a man with a really good mind on the job. However, they take a while to show up, and then we don't know they're the bad guys apart from menacing music; but once they start doing their thing, the questions start coming.
There's a lot of intensity in the film, even if the scenes aren't action. For example, in one scene, McClane's slowly climbing down a ventilation shaft, using his gun and its strap as rope. As he reaches for a vent, we're treated to several shots of the strap slowly... slipping... out of the gun. Even when he's in the ducts, his troubles aren't over. A Genre Savvy
terrorist assumes he's in the vents and perforates a ceiling duct - which just happens to be the one McClane's in. He narrowly misses, but starts feeling if someone's in there, and gets called off just in time. Stuff like this keeps the film rolling until the end.
Part of what keeps everything so tense is our astonishment that McClane's still standing, even after getting beat up numerous times, shot, and even running across broken glass in bare feet. He'd like nothing better than to just sit and wait for the police to solve everything, but by then it'd be too late - it's all up to him to stop the bad guys, so he keeps on truckin'.
Throughout all of this, part of what keeps Die Hard
good is the fact that it never goes too over-the-top. Everything stays relatively believable, bringing the action down to earth, or at least the top of an office building.