Instead of making an enormous post going into major details, I'll just list a couple and reasons behind it.
Shin Megami Tensei (Tracks that complements it's settings while also being very catchy)
Pokemon Mystery Dungeon (Nice pieces for exploring that don't get annoying over time, and some great themes and one-shots)
Nier series including Drag: On Dragoon (Unique and rather unsettling at times)
Xenoverse [Gears, Saga, and Blade] (Great game OSTs full of passion, exploration, fun, emotion, and the like)
Pokemon (just in general. Grew up with it and love its tracks)
Mario Galaxy Duology (Great Orchestral and other nifty pieces)
Metroid Prime Trilogy (So many great space themes and otherworldly pieces. Plus I second on the menu themes for 1 and 2 being amazing)
Mario Strikers Charged (So much personality crammed into a really good sports game)
Persona (Technically in Shin Megami Tensei, but its tracks tend to be different in tone, style, and point to them)
Silent Hill (Especially 2, so atmospheric and messed up, it's great)
Hyper Light Drifter (Better when playing in-game, but the rather soft pieces that play as you explore just never gets old for me)
Dead Cells (My favorite game soundtrack. I love every piece in it and never get tired of hearing them as I die and try again to make a run)
Hollow Knight (Good lord is is atmospheric and mood-setting, especially Dirtmouth and City of Tears)
Mario Party (An odd one to say, but they've got good tracks all throughout their entires, especially the board themes in my opinion)
Daemon X Machina (Hit harder than the boss's attacks)
F-Zero (A futuristic boppin' soundtrack that just hits so right and has an identity of its own)
Fire Emblem (Even the lacking entries just have such good music that satisfies my medieval itch)
Kingdom Hearts (Yoko is amazing and even some of the newer and other composers do a good job too)
Shadow of the Colossus (Really makes you feel small in an amazingly large world with huge beings you need to climb)
Sonic the Hedgehog series and other entries (Just a fun time to be had)
Zero Escape Trilogy (The perfect track for a series that mind screws you so much)
Smash Bros remixes and originals (Well done, Melee and Brawl hold the most remixes that I like)
Soulsborne series (So many good boss themes from all the games)
Dead Space series (Everything about this screams danger or ominous as you potentially get attacked)
I think that's enough for a post.