Super Mario Sunshine, Cave Story, Shovel Knight Treasure Trove, Wind Waker, Ocarina of Time, ACNL, Mario Kart 8, Super Smash Brothers Melee, Super Smash Brothers for Wii U...
Some of my favorite OST's comes from Splatoon (2), Pokemon (especially Mystery Dungeon), Animal
Crossing, Super Mario Sunshine, Luigi's Mansion, Harvest Moon (especially A Wonderful Life9, Mario
Kart 8, Sonic Adventure (2) and Crash Bandicoot.
Final Fantasy Crystal Chronicles and Ecco the Dolphin comes to mind. Otherwise I can only think of single songs from various games (recently, the Subcon Forest "off path" track from Hat in Time has really stuck in my head).
Jet Set Radio and Jet Set Radio Future have probably the best soundtrack ever. Hideki Naganuma's remixes are amazing and they choose some of the best artist to include. Cibo Matto and Guitar Vader are love.
I actually created a playlist of all my favourite OSTs (and some other random animevibe songs and stuff) to help me be more productive when I can't think.
Undertale... It's so good. Every song is ridiculously catchy. I find myself always coming back to listen. I also really love Yoshi's Island (SNES)'s soundtrack. It gives me nostalgia of playing it when I was young. (*?꒳`*)
Oml Xenoblade Chronicles for sure. I cannot express enough how amazing it is. Agniratha (Day) is my favorite, so much that I cried the first five times that I listened to it, I was overwhelmed by how beautiful it is. Of course this is my opinion, but I still recommend giving the four hours+ OST a try.
Of course there's amazing stuff like Smg 1-2 but rn ill just say PUYO LUYO TETRIS / CHRONIC L E ( honestly idk how you would type out the Jap pronunciation of chronicles )
I usually only notice videogame soundtracks when they work their way into my brain earworm style from playing for too long and therefore become annoying...
but the ACNL music is all fantastic and so relaxing...
(Kirby's Epic Yarn = very relaxing music too heh)