Ah, this was tough one, since I played quite a few games when I was little. But, I’d have to say the Threads of Fate/Dewprism OST would be the most nostalgic, even though it wasn’t my 1st game, nor my 10th.
The soundtrack has a lot of good songs on it, but I chose Passing Through The Forest/Carona Forest, for this day since it’s the first true level you play, and people tend to remember it more than any other track.
Others to listen to from Threads of Fate/Dewprism:
quickie Dewprism fanart. The character designs were so cute, love the badguy and his weird metal pointy nose mask
This game influenced me a lot as a kid !!
(though admittedly for reasons I cannot figure out and are probably tainted pretty heavily by rosey nostalgia, because my partner and I have been playing through it and we’re still stuck at those infuriating timed jumping minigames at Fancy Mel’s)