Persona 3 came at just the right time for me (although, to be fair, I had played and liked the first Persona also).
It's disappointing how stagnant the formula has become since - it's still largely the same template from more than 15 years ago, though it's obviously been polished since then. Persona 3's pacing isn't great, but it doesn't indulge in many of the anime stereotypes its successors do (although Kenji's social link is memorable, it's mostly about
just how bad a decision he is making) and the core of the Press Turn variant the series has used since is already there. In retrospect its AI-controlled companions made it stand out in that you have to rely on your teammates to make good decisions (although you can guide them). It was notorious enough to spawn several popular memes, but honestly nothing that bad ever happened to me in my two playthroughs (base then FES Journey) - and the ability to ask your team to split up was an interesting innovation. You can kind of see where a different sequel could've gone with "one of a team" instead of "the star of the show", but they seem to veer more into power fantasy territory with each entry.
Persona 3 also has a subtler cast relative to its sequels, which I think is one of its strengths - it takes a long time for them to trust you beyond fighting shadows together, and by the time they do it feels earned.
Although I liked P4 at the time, and P5 was okay, Persona 3 started it all and IMO has the strongest core plot - which isn't that surprising to me, because in addition to copying core mechanics, the core concept of
Society's ills causing problems through collective unconsciousness stuff
also recurs in the sequels, and it becomes more rote each time.
