P.S: Ignore any typos. And grab some snacks because it's a very long review.
My review will be quite long (too many good things about One Piece) but I will include a shorter/summary version at the bottom if you don't have time. But I suggest you go through it all :)
Let me start with the negatives, which is only one and is only concerned with the Anime.
Negatives: The Anime has terrible/painful pacing, especially during the Skypiea, Thriller Bark, Punk Hazard, Dressrosa arcs. This however, is exlusive to the Anime version and can be overcome by skipping through episodes, skipping fillers (if you wish), etc. So it's not too much of a concern. You'll just have the trouble of waiting for at least a week just to get an episode that cover one or less than one chapter (which is quite less).
Now coming to the pros. There are a LOT of amazing things about One Piece.
Plot (10/10): The plot of One Piece is the single largest plot of any popular anime that has come out thus far. I say this with confidence as other long running series like Detective Conan, Hajime no Ippo (which are very good themselves) have a narrower plot. One Piece has phenomenal world building. Without spoiling too much, it occurs in it's own UNIVERSE and time. In terms of the vastness of the setting, only Dragon Ball Z comes close.
There's several hundreds of different/unique powers. Most of these powers (including that of the protagonist) are completely fresh/never before seen anywhere, not just in anime. (And no, it's not just Devil Fruits)
The plot intensifies exponentially and increases in complexity as it progresses. The first 100 episodes, it's just the pirate Monkey D. Luffy, the protagonist, and a his first few crew mates sailing to find the One Piece, a legendary treasure that has been left at the last island of a harsh, destructive Ocean called the Grand Line. But soon we realize a lot more. In the next 100 episodes we learn more about the ACTUAL plot. By the 200s, we have a very well established plot line, but it still grows. In the following 100-200 episodes we learn much more..and so on. By the first 400 or so episodes, the setup is done and everything that follows is just pure awsomeness. With every passing arc, the story gets better and better. However, there is on not-so-important arc which is mostly for comedy which I personally loved (like almost every other One Piece fan, so you probably will too)
People often complain about how long One Piece is, but let me tell you this, that's how big and vast the plot is. It REQUIRES time. You will have to be patient. Everything that happens in One Piece happens for a good reason, but it does take time. So be patient and try to watch as many episodes as possible. You can binge watch it and finish it in 3-months (Like I did) (as of 28th March, 2016) or watch it slowly over the course of a year.
The plot is always, ALWAYS filled with mysteries. Some answered soon, some so EPIC that we can only learn of them when the series reaches it's end. This is one of the things that keeps me going.
It always has comedy. Many many epic moments and even more to come (it'll be obvious once you catch up to either the Anime or the Manga). Honestly, I've been a One Piece fan for very little over a year now but I don't see myself disliking it ever. I have more than enough confidence in Eiichiro Oda's story writing that was built through 734 episodes and 820 chapter (and still counting). I was never disappointed with any aspect of the plot of One Piece (Except maybe one, but that's completely insignificant). One Piece has many great/amazing/epic fights. However, let me warn you, there's many mediocre/decent to good fights as well. I would recommend Dragon Ball Z, Hunter x Hunter, or Naruto for fights. The fights in One Piece are are not as good as in these but are still very good and enjoyable so no worries here.
Even if everything else (art, sound, fights) were terrible, (which obviously is not the case. It's the exact opposite) the plot alone is worth a 10/10 overall. Trust me. There's a 90%+ chance that you will feel the same.
If you've heard someone say "One Piece sucks, no one dies" do not believe them. They probably watched only a few episodes. Another great thing about One Piece is that only characters that matter the most die. And as I told you, the plot intensifies exponentially, this means character deaths are ever increasing (but not by much). But this is as far as I'm willing to go into this.
Also, contradictory to what some might say, One Piece is not repetitive. There is always a reason for why something happens and its almost always different. So be prepared for an exciting, adventurous, enjoyable, funny, action packed, suspenseful story...I mean epic. That's right, One Piece can be considered an epic. That speaks for it's complexity.
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Characters (10/10): One Piece is filled with several amazing characters whom you will love and several others whom you will hate (amazing evil-minded, hateful villains).
Shanks, an amazing character introduced early on, has in fact inspired the creation of a very popular character in another series! Gildarts from Fairy Tail.
There's a vast variety of personalities you will find in One Piece. and many important characters have great character development. Both the antagonists and the protagonists have great moments and undergo proper development.
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Animation (7/10): The animation of One Piece is not good. However, epic moments, epic fight scenes, etc. are almost always very well animated. The infamous Marineford arc has almost movie level animation! If you don't believe it, watch it! (Full of spoilers though, obviously) The animation is great when required. Other times, it's quite still and stocky. But this shouldn't be much of a concern either as the important parts are seldom badly animated. The series goes HD somewhere near the early 200s because it started in 1997 so don't judge it too soon :P
You can look up Naotoshi Shida scenes in One Piece. He is a very famous animator and has created several beautifully animated scenes for One Piece.
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Art (9/10): You must've heard, One Piece has a very unique art style. It has heavily exaggerated character designs (which I've come to love). I mean the badass characters look badass as hell, gorgeous characters look absolutely gorgeous, ugly characters look ugly as hell, etc. If you're new to it, you're in for a surprise. It's unrealistic yet epic. Plus whoever said unrealistic = not good? One Piece is evidence against that xD
The backgrounds are always amazing and full of detail. There are thousands gorgeous shots/panels.
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Sound (9/10): The One Piece soundtrack is also one of my favorites. The background scores fit the situations perfectly. Suspense building, action, adventurous, uplifting, you name it. There's tracks for all this. It's heavily orchestral. I often find myself listening to the soundtracks as they are quite epic.
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So yeah, that's it. Overall, One Piece is superb, excellent, amazing, awesome, etc. Few downs here and there but those are very insignificant in comparison.
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SHORT VERSION
The plot of One Piece is absolutely amazing. It grows in complexity as it progresses and is always filled with intriguing mysteries. The main plot line is more than just finding treasure and becoming the Pirate King. It's unbelievably huge. One Piece has a vast setting and amazing world building with epic, unique powers that were never heard of before. There's always comedy, adventure, action, mystery, and fun in One Piece.
Due to it's vastness and complexity, One Piece is very very long. However, ignoring the bad pacing of the Anime (only) it is never boring.
If you feel like an episode is being dragged, forward it, or skip through a few stretched parts (Like 30 seconds of smoke, 5 minute stare-downs, 6 minutes of recap, etc.) The slow pacing can be easily overcome.
Everything in One Piece happens for a reason, and it is seldom repetitive (contradictory to what a few others say). Has many great fights that are often very well animated. The infamous Marineford arc has almost movie-level animation. But fights aren't it's strong point (though they are epic).
If you've heard someone say "One Piece sucks, no one dies" do not believe them. They probably watched only a few episodes. Another great thing about One Piece is that only characters that matter the most die. And as I told you, the plot intensifies exponentially, this means character deaths are ever increasing (but not by much). But this is as far as I'm willing to go into deaths.
Amazing variety in characters. There are characters whom you will absolutely love, and others, like villains, whom you will hate (in the good way. Evil villain = more hate). And there's villains who are badass as well. Many intriguing personalities and backstories. Great character development
Art style is unique and character designs are almost always amazing. It has heavily exaggerated character designs (which I've come to love). I mean the badass characters look badass as hell, gorgeous characters look absolutely gorgeous, ugly characters look ugly as hell, etc. If you're new to it, you're in for a surprise. It's unrealistic yet epic. Plus whoever said unrealistic = not good? One Piece is evidence against that xD
Has very good soundtracks that capture the moment perfectly.
One Piece can be considered an epic. That speaks for it's complexity.
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One Piece has quickly grown to be my favorite shonen anime. I hope you enjoy One Piece and one day we could probably spend hours and hours just talking about it.
Patience is key when watching One Piece. But you will most probably get hooked to it pretty soon. But make sure you have time.
For those on mobile
Story 10/10
Art 9/10
Animation 7/10 (Damn you Toei Animation)
Sound 9/10
Characters 10/10
Enjoyment 10/10
Overall 10/10 (Plot is absolutely amazing. The characters, the comedy, the adventures are all very very good)
