Old as it is, this is still a good topic.
I'm torn between Persona 3 and 5.
Persona 2 IS is a strong contender, as that game had a lot of interesting elements. It had a solid quiet protagonist who got stuck in a bad situation, and it has a rather natural flow to the story of you falling into the plot, while making friends of enemies, while dealign with an interesting take of "yours words have power"
It was nice having EVERYONE be a Wild Card, while also having the power of persona in real life, instead of having to have a gimick to activate them. I didn't care for EP as much, and had a hard time staying with it.
Persona 3p was my favorite for a long time. I didn't care for it much because of the people around me non stop drooling over the game, so it dissuaded me from even trying. Years later, I got the game at a discount, gave it a try, and started to kick myself over how good I found it. i later found out the differences between this and the PS2 titles, and I was a bit saddened by the loss of animated cut scenes, but I didn't miss actually walking between locations. I felt the menu driven movement kept the game fluid, and minimized keeping you away from both the story, and action.
The theme of the game being so dar was a refreshing change of pace from what I was use to, and overall felt clean. It was interesting building bonds with players, yet you didn't really feel connected to them. Even at the end, Door-Kun felt like the lone wolf, and he was just there to kick ass. I liked that about him. He wasn't connected to anyone, bonds aside, and he was the one everyone ran to for help.
Persona 5 was a game that resonated with me, because I was in a bad place when I tried the game, and was starting to strongly hate the justice system, as things kept happening around me that felt like people were getting away with shit and there was nothing I could do without getting in trouble my self. P5 was the release I needed as it spoke to me, so it was a game I fell in love with. The Acid Jazz, the theme, the story, and how the game played were all very addictive, and I liked actually going after trouble, instead of waiting for trouble like the other entires.