It is my opinion that persona 3 is the worst of the 5 (6) Persona games.
Here is a link to a post I made about why persona 3 kinda sucks. If you want to quit, I think its fine. I didn't like the ending (though some did). That said, you're likely closer to the end that the beginning by being 40 hrs in.
>And is Persona 4 worth to play after?
Persona 4 is the comfiest game of all time. It has the best girls of the 3 "modern" persona games (all 4 party girls are great, and 1 is waifu-tier). The story is not overly complicated yet still good. The music fits the country-town japan atmosphere that the game portrays. One of the things I love so much about p4 is that it doesn't take place in big metropolises like other weeb/jap games. The interpersonal relationships between the characters and side stories/social links of each character in p4 is FAR better than both p3 and p5. The only gripes are the simplified combat and simplified dungeons (game is still difficult if you play on hard or very hard difficulty). I think P4 is much better than 3. P5 ended up trumping P4 in everything but overall girl quality (though makoto is a cutie
) and overarching plot.