ah, this is. Very hard. Video game ost, my favorite genre of all time. And I love so many osts. Hmm, let's see.......
Kind of a weird tie between Legaia 2 Dual Saga and Legend of Dragoon for my current number one ost. I listen to both a lot (also yes I like Legaia 2's ost a tad more than the first game, I legit don't care what the elitists from that fandom say, Legaia 2 was a good game and I adore the ost). I probably go out of my way to listen to the Legaia 2 ost more often, but I replay Dragoon once a year, so the amount of time I spend listening to either ost more or less evens out.
LoZ...LoZ all the osts, not a single bad LoZ ost....but okay, TP is probably my fave LoZ ost too, although I will note Skyward Sword is a very close second. I don't talk about Skyward Sword hardly ever but I love it dearly, and several tracks from the SS ost got me through so much college homework.
FE has so many good osts, but the osts for Echoes Shadows of Valentia and Engage are probably tied for me (just as they're tied for my fave FE). "Song for Bygone Days" from SoV is one of the best and most haunting world map themes I've ever come across, and "Twilight of the Gods" is one of my favorite final boss songs ever, but all the songs associated with Lumera (esp. "Flash of Distorted Light") are so good, and I also really love all the songs associated with Veyle and the Hounds like, "Crimson Black" is just haunting.
Castlevania Curse of Darkness was the Castlevania ost that introduced me to Castlevania and it has such a dear place in my heart as a result. Absolute banger of an ost (not a bad Castlevania ost out there either, although I also really love Lament of Innocence and Symphony of the Night as close second and third faves).
This is gonna be out of left field but there's this ancient game for the PS1 called Darkstone that my mom played A LOT when I was a kid, and that ost is like, honestly one of my top favorites despite there not being anything outstanding about it, I guess? I dunno if it's nostalgia, or that I've never found a song that hits like the main Town theme does, but I love this ost to bits and pieces so much.
Special shoutout to these osts I also love and adore, in no particular order: Gauntlet Dark Legacy, Octopath (1 and 2), Live a Live, Illusion of Gaia, The Last of Us, MGS (all games), Okami, Super Metroid, Ender Lilies, FF7, Paper Mario The Thousand Year Door, also not gonna lie I'm only a handful of hours in but Expedition 33's ost will probably be one of my top faves when I have heard all the songs.