Final Fantasy overall is so great in this department so I can't just choose only one song.
The first one that comes to mind is
Melodies of Life rendition from Distant Worlds. I love the lyrics so much. Susan is so strong is her delivery here too.
Couldn't make this without a song from the original FFVII, a game that makes me so much emotional for a myriad of reasons, even 23 years after. Hell, I am emotional just now listening to it.
Tifa's theme is so pure and beautiful and had that air of nostalgia and melancholy.
FFXIII is really divisive and for some good reasons but I always find hard to argue negatively about it's OST. For me it makes justice to Nobuo Uematsu and the game came in just the right moment for me when I played it. Also, ignoring XIV it was the last FF game I was really moved. And FF at that point was still my favorite series. So yeah,
Serah's Theme and it's multiple variations still hits me pretty hard
And the last but not least,
this version of Memory of the Wind. I just love it. It have that old FF magic for me. I love III so much, always find it underrated along V (that could make the list too with Dear Friends).