Dredd, but my reasons are more from a writer's perspective. Although the directing, cinematography, acting, and soundwork, sets, and everything else are done with with no mean skill; more on that in a moment.
There is a saying that perfection is achieved not when there is nothing left to add, but when there is nothing left to take away. When it comes to modern action movies, most fail to heed this advice. See also Micheal Bay, whose formula is usually...not a stunning success. (Though he has his moments; Pain & Gain as a satire is amazing.) Most are also...well, they're aimed at wider markets, and hence not always very good as action movies.
There are exceptions. The Raid: Redemption is a personal favorite of mine, though it's too much action movie for some people. The recent Mad Max: Fury Road is in the same vein.
And then, there is Dredd. If perfection is achieved when there is nothing left to take away, Dredd is the perfect movie. Everything you see, everything you are told, is meant to tell you something. Sometimes what it's meant to tell you isn't very deep; the line about the reopening of the food court, for example, isn't meant to say much beyond the fact that yes, they reopen fifteen minutes after the bodies are cleared away because society doesn't care very much about a mass shooting. The names of the various megablocks are references to various things.
But before the opening is even complete there's a very important scene, which doesn't pay off until much, much later in the movie. That's the kind of movie you're watching. Everything matters. Everything is meant to matter. You may not see it, or it may go over your head (a lot of it went over mine until I actually read some Dredd comics or watched the special features on the DVD), but it's there. The nonsense-word on the back of one guy's shirt from the opening chase? Doesn't mean anything to most of us if we even see it. Authentic swear from the comics to those who get it. A small signpost for how well the team knows its Dredd lore.
