Undertale, love the Temmie Village song. The OST can be heard in all kinds of videos. Maybe since you liked ULTRAKILL (based on graphics), you’ll like Undertale.
NieR:Automata is an absolute banger. It has a banger of a soundtrack and a really great story. I personally love the park area and the forest.
Subnautica, the OST, really helps to create an immersive experience. It is sometimes mysterious, it can be dark but also adventurous. The music kind of guides you through the uncharted lands.
The Legend of Zelda: BotW I know, it’s a WIIU/Switch game, and I know TotK is out, but the design and the music of the game are fitting so well together. The OST is so incredible.