Any drama needs to conform to the dramatic curve of increased and decreased tension. That also goes for thrillers, action films, horror stories, and so on. Basically they're all drama, from a narration perspective.
Now, the drama that gets us hooked from the beginning to the end has a curve of tension or excitement, which is almost the same in every successful drama. The simple form of this curve is the exponential increase of tension all the way to the climax, after which the tension drops to almost nothing as the closing scene unfolds. It looks something like this:
|The dramatic curve.|
It's needed, because the climax leads to the solution, and after that the audience is impatient to exit.
In a refined drama, the curve gets more complex. It can start with quick initial excitement, just to grab the attention of the audience. Then it drops to low, followed by a slow increase – maybe with some short drum beats of tension on the way. But the general figure of tension development is still basically the curve above.
The film Taken failed completely to follow that curve. It started slowly, like a thriller usually does, but at the moment of the daughters kidnap it went up high and remained there all through. Were it not for the very competent acting of Liam Neeson, we would have lost interest long before the end.
He was an interesting hero – a seemingly loving father with a raving mad capacity. That's why an audience would not be disappointed until the end, which was simply finding the girl and killing the bad guys. Exactly what he set out to do.
In that way, the film also failed another basic law of drama: the development of the protagonist. For the audience to stay enchanted by the story, it has to show some major development of the one who is the real main character of the story – often not the obvious hero. Someone has to learn something, discover something, or accomplish something previously deemed impossible for him or her.
Nothing of the sort happened in Taken. The father-hero just went on with his rampage until he saved his daughter, and then everybody was happy. Nobody changed significantly.
That doesn't work. We may still see the movie through, but we forget it the moment the end credits start rolling.
Aristotle told us more than two thousand years ago: there are rules to drama. If they are not obeyed, the story collapses. It's odd that Luc Besson, the merited film maker who was one of the script writers, failed that basic requirement.