First and foremost is the interaction between Ellie and Joel, first having Joel loosing her daughter in the initial sequence gives a great background to Joel's character in the story development, this is boosted somewhat by making Sarah playable in the initial stage of the game which showcases the bond between her and her father and how abruptly that relationship ends with Sarah's dead.
Then we find what Joel became 20 years after the incident with Sarah and how he denies or ignores her daughter dead, to find himself pushing away Ellie which is pretty akin to Sarah.
Onwards the story presents several character arcs, and the setting by which these developments take place is really grim, savage and gory. Which builds up an incredible momentum of drama that gives a constant state of tension, without overwhelming the narrative and the pace.
This game is a great example of how to manage pacing in games, the action exists but is never too excessive or too repetitive or too calm, and the finding/scavenger/crafting mechanics are very well design which fit the theme that the game is going for.
The ending is incoherent for anyone but Joel, which is one of the most emotive moments because having play through his moments, the moments he had with Ellie and knowing what kind of losses he suffered, is logical to assume his decision, which really does set the bar in how storytelling should be and should go.