Persona 4 takes everything you loved in P3:FES and gives you brand new characters, story, and refined gameplay - Winner!
First, if you're a fan of Persona 3, a word of advice: stop reading, close your browser, and buy this game! Everything you loved about P3 is back in P4, but with all new characters, a new setting, a new main storyline, new Personas... enough is new to make it all fresh and fun again.
For those that are new to Persona, I will attempt to give you a taste of what this game has to offer.
Some of Persona 4 is standard JRPG-fare: plucky young heroes, mystical and often bizarre enemies, turn-based tactical combat, and a strong Japanese social identity. However, from there, you can throw your expectations of JRPGs to the wind.
The game centers around a teenage male hero (voiceless, named by you) and his friends as they attempt to solve a series of bizarre murders that appear to be tied to a parallel world shaped around the inner thoughts of people in our world. While solving the mystery, you will still need to live the life of a teenager:
1. Attend high-school -- You'll actually be thrown questions from your teachers about math, English, and geography that, if answered correctly, can boost your character's stats. You can also attend school clubs and athletics, go to the library, etc., all of which will boost your stats.
2. Cultivate friendships -- Your Personas (more on those in a moment) will become more powerful if you spend game time cultivating strong friendships with your party's NPCs. This may involve spending the afternoon with a friend or simply replying in a thoughtful way when they speak with you. Your stats will improve, and you'll even open new quests and partners this way.
3. Take part time jobs -- You need money in the game, which you'll get in combat. But to really get enough to deck out your party, you'll need a job which will also teach you some minigame skills you'll need for quests.
4. Explore the town -- You'll buy equipment from shops, eat at restaurants, etc., and all of these actions affect your character's development. (For example, you can boost your Courage by eating a spicy meal...)
There are even more potential actions and events than these throughout the game world. Each day that passes in the game world requires you to choose how to spend your time, which will cause the game to unfold quite differently each time you play.
However, the most important (and most fun) activity you can choose is combat -- you spend an afternoon in the parallel world in order to continue solving the overarching mystery, and save people in peril. Within that world, you will encounter demons to fight, find clues about the main story, etc. There's good variety in the creatures you'll face -- sometimes even alter-egos of characters you meet in the game. Combat is done by either using traditional weapons, or through your powerful Personas. Personas as basically summoned super creatures that appear, perform a super attack (using Magic Points), then vanish. They level-up just like your character, and you can collect and combine them in interesting ways to change their abilities. They are acquired by collecting Tarot cards in combat. The Personas have astrological signs that help define the very complex metrics through which they'll gain additional attacks and defenses to help your party, and how they increase in ability.
I could delve further into the game play, but more than half of the fun of Persona 4 is discovering all there is to see and do in this world -- and despite all that I've said here, I've mentioned only part of what there is going on in the game.
Visually, it is likely the best-looking PS2 game I've played, and the overall style of the game's visuals are striking and exciting. The art in the game is either nicely detailed hand-drawn images, or well-rendered 3d models (remembering that this is the PS2, not the PS3...). All of your character movements, combat visuals, and most environments are in a third-person 3D view, and everything is smoothly animated.
A unique musical score is one of the highlights of the Persona series. P4 carries on the tradition: the soundtrack is a mixture of J-Pop and a traditional orchestral score. The music sets the tone of the goings-on quite well, and completes the atmosphere throughout the game. About three-quarters of the game dialog is spoken, and is very well acted, though over-the-top for the main foes (a typical trait for JRPGs...).
For those that have not enjoyed the previous Persona games, nothing will win them over here. Likewise, if you're looking for a traditional Japanese RPG, you may be a little overwhelmed (or just weirded-out) by this game.
Even for the fan, there is one big hurdle to clear - the initial exposition of the story, introduction to characters, introduction of some of the game mechanics, etc. unfold over the first 2 hours and 30 minutes of Persona 4. This 2+ hours of time is spent with very minimal interaction - most of your time will be spent viewing in-game cut-scenes, listening to dialog, and being given very short tutorial-level interactive moments. This game is not about diving in and fighting it out - it's entirely about the game world as a greater whole, and pulling you emotionally into the 60+ hour overall experience ahead of you.
However, for those that are more adventurous and looking for a deeper, complex RPG experience, you will be well rewarded.