I jumped in with P5, so I don't have full knowledge of the OSTs.
Here is a lot of great persona songs all in one place.
All the music in Persona is great. In my opinion P3P had the best sound track. I love all the songs from P3 and FES, but the FeMC's songs are fantastic all on their own. Her battle theme is my favorite from all of the games. I love the opening song for P3P it is great. And I still get the feels from Memories of You. (The Credits Song)
Choosing just one from the persona series is a challenge in itself because of how excellent the soundtracks of each game are. The animation also have amazing pieces placed in them as well so it just adds to the difficulty. I have to say "we are one and all, light the fire up in the night, bloody destiny, break in to break out, Infinity, and unbreakable tie have to be in my top favorites from the series
Literally every Persona boss theme ever, my personal favorite is Innocent Sin 's boss theme.
Nyx's theme Battle for everyone's soul
What do you think?