Part of what made 2011's Bastion so popular was its sense of scaling. The game builds up gradually, level after level, establishing a sprawling story as you forge forwards, ever into the unknown and the unaccounted for. The game's soundtrack reflects this, with tracks that build towards grand cacophonic endings that leave you feeling exhilarated.
Kingdom Hearts 2
From the serenity of "Dearly Beloved" which many will recognize from the title screen (and other times) to the severity of One-Winged Angel with its intense, high-energy and impact, the OST for KH2 is an amazing accompaniment to the game. The score helps to define key moments in the narrative, and really drives the action sequences when it is called upon. It balances between dark and light, keeping in context with the game itself.
It would be doing a disservice to everybody to leave this game off of this list. Journey is, from start to finish, a very intensely musical game. Every interaction you have with the world around the player-character is layered with music, and the theme of the owrld around you builds to the music you create with your actions. The score is beautifully wrought to evoke that feeling of smallness and wonder in the listener.
I dare you to find a more fun, silly, upbeat and whimsical soundtrack than the soundtrack of Katamari Damacy. This game has risen to cult status with the people who are devoted fans of the series, and a big part of that is the musical aesthetic of the game. Full of energy and happy feelings, the soundtrack is just totally awesome. "Lonely Rolling Star" is just pure fun and joy.
Shadow of the Colossus
Okay, so maybe I have an unhealthy love for Shadow of the Colossus. Or, then again, the game is just too amazing for me to ever stop loving. Or writing about. Or replaying. In any case, the game would only be half as amazing as it is without the soundtrack to accompany it. The sprawling Forbidden Lands would feel that much emptier if not for the music in the background, and the fights against the colossi would feel less spectacular were it not for the triumphant bellowing of the orchestra behind your every action.