Funny how neither you nor I brought up Stickerbush Symphony, which is the most praised DKC theme, maybe only topped by Aquatic Ambience . I personally find it a little bit overrated. Now, one that is really underrated: Hot-Head Bop

I wanna give a shout out to the Crash Bandicoot franchise, specially the Twinsanity's OST. They used acapella songs and the result turned out great. My favorites are:

https://www.youtube.com/watch?v=0OIqlp2U9EQ

https://www.youtube.com/watch?v=p5CZZ_LugJo

https://www.youtube.com/watch?v=qgz9Y-YPZXc

That, I agree. Undertale has a phenomenal soundtrack (and Deltarune is giving it a run for its money... and the game is not even finished yet).

Shout to Fatal Frame for the incredible theme songs by Amanio Tsukiko:

Alan Wake only has 3 games so far, but the soundtrack is already at the top of my list.

I concur with the mentions of Final Fantasy, Crash Bandicoot, and Alan Wake (and probably would about many others too if I was more familiar with them). I'd like to mention Dynasty Warriors as well:

Touhou games also seem to have great music, although I haven't played any of them. I've run into an insane amount of great Touhou music though.