The gameplay elements are integrated into the storytelling in a way I can only describe as art. Desolation, terror, desperation, and triumph experienced in the gaming elements are as well integrated into the story as the best soundtracks are integrated with the best made movies.
The experience of holding on by your fingertips, as the grip bar shrinks, the horror experienced when scoping out the 8th colossus from a distance and letting it close with you, the hopelessness of operating the last character to appear... these are all integrated with the emotional intent of the part of the story they are in, to the point where the gameplay is integral and not a bolted-on gimmick.
Interactivity is just another element, like color, sound, music, CG, 3D, or any number of technical innovations. It's just another tool to be used, artfully or clumsily. It may start out as a gimmick, but creative and talented people will figure out how to properly integrate it over time.
(Yes, soundtracks, color, CG, and 3D were once all pronounced to be gimmicks that added nothing to the art of movies.)