The first Maze Runner was something to behold: a YA adaptation with no introduction of love triangles, little adolescent angst and very exciting action scenes. It consisted of little more than teens outrunning giant mechanical monsters, and it was amazing.
The Scorch Trials expanded the scope of the story and the settings, so it suffered a bit. The introduction of villains and the required end of the world stuff was not so exciting, yet the movie still found room for kinetic, non-stop action scenes.
The Death Cure is the weaker of the entries, with even greater emphasis placed on the villains whom are not as interesting, or compelling enough to share frame with the protagonists. There are fewer action scenes, but they remain competently made as ever.