There's a lot of stuff about Persona 1 that I think is just really cool. I like how you get the vibe that the cast have been friends for a while long before the game begins. Most RPGs don't really have you jump into an existing friend group like P1 does. What's also really interesting is that there's a choice of like 4 characters for who the fifth party member will be, with this actually affecting the story a fair bit and the optional party members not feeling as though they're just haphazardly tacked on. There's also an entire 2nd story route called the Snow Queen's Quest that's basically a shorter harder dungeon crawler route, while I wouldn't call it essential to check out, I just think it's super cool that they went through the effort of making it, since it's really the sort of content that if it was made today would probably be relegated to $20 DLC.
It's also funny with how big a deal the other Persona games make about how special and rare it is to have a Persona that in P1, Personas are basically given out like candy incredibly easily. Like being a Persona-user in P1 is such a common mundane thing and it's hilarious.
Also, I adore that Mark canonically brings a battleaxe to school everyday, since he's the only party member who starts with a weapon equipped.
While P1 is definitely a flawed game, it's overall message hit me hard and helped me through a tough time in life.
Also, while this is probably a hot take, I prefer the PSP OST. While I think that the OG PS1 Soundtrack is definitely the better collection of tunes, filled with an absurd amount of tracks that are just there for a single scene, the worst tracks of the PS1 OST are the ones you're going to be listening to the most frequently. While the PSP's OST is overall weaker and cut out so many awesome unique tracks and butchered some others, they made sure that the tracks you're going to be hearing most often sound good. While I'm not even the biggest fan of Lone Prayer, I vastly prefer it to the regular (honestly kinda bland) PS1 battle theme. Also, School Days slaps.
Also also, I adore its cover art, definitely an all-timer for me.