"This Man" is about as standard plot-wise as action movies get. A lone wolf type takes a little girl under his wing, the kid gets kidnapped, and he ends up having to go through heaps of bad guys in his quest to save the girl.
By all accounts, the movie should have evoked little more than a shrug. After all, anyone who has seen even just a moderate amount of action movies will have seen countless movies with variations of this basic plot. One might think of "Leon" or "Man on Fire" for some closer examples, or movies such as "Taken" in other respects.
What made this movie into my favorite action movie in a long while is the execution of that basic plot. "This Man" manages to create just the right dark, gloomy mood to match the story and all the characters are believable. None of the scenes appear contrived or overly tear-jerker. Another vital aspect for an action movie is, of course, that the action sequences are very well done. The movie is quite graphic, but not gratuitously so or for its own sake such as in many a recent horror movie (the Saw series comes to mind).
I guess the movie could be likened to a good apple pie - certainly nothing revolutionary, in fact quite the staple of its genre, but who would want to turn down a really good apple pie with quality ingredients?