Know this, its a fantastic manga. 80-90% of the people who don't read it are people who were influenced badly by the art or the horrible 4kids dub which destroyed its image or just had trouble getting past the slow beginning. But people who truly don't like the series aren't that common.
Don't judge this one quickly whatever you do. Read 100 or even 200 chapters before giving up on it. Most people start liking it after the Arlong park arc, and then completely fall in love with it after the Enies lobby arc.
Synopsis: The story is about Monkey D Luffy and his quest to become King of the Pirates by travelling the Grand Line and finding the legendary treasure known as One Piece.
Story: 9/10
Pre-grand line the story isn't really that much and was all just character development. Some very heartfelt and beautiful flashbacks to each of the crew members pasts. They had some horrible incident happen in their lives which made them outcasts, but Luffy recognizes there strength and gets them to join his crew.
When they enter the grand line its still mainly about developing new characters, but Oda starts to tie the world together a little bit. The existence of the forbidden pone-glyphs, the corrupt officials in the world government. All this starts to tie itself together in the grand line.
The story itself is also a real tear jerker. I get lumps in my throat all the time listening to them. Keeping in mind that I am an emotional robot so you will probably end up grabbing a Kleenex.
power-ups I would say are done somewhat poorly. At least the first wave of power-ups during the Enies lobby arc. I would say they are 5/5 for "cool power-ups" and 1/5 for well thought out power-ups. Oda just had them evolve out of nowhere without any foreshadowing. The next power-ups though were absolutely perfect. After the time skip, they had basically been foreshadowing the abilities and changes to the crew for the duration of the manga. Absolutely perfectly done.
Another thing I have been noticing about the story. Oda is actually building towards a sequel. He's left all these hints talking about things the pirate king did and they never go into much detail but Oda leaves it open to be elaborated on in a second one piece manga. Its rather epic and grand when I think about it. That he's already putting together a sequel about the original pirate king.
Art: 10/10
Original art style designed specifically to work with the pirate theme. This turns a lot of people off, but you can't possibly claim that Oda is actually bad at drawing. Looking closely at the pictures there is so much detail in every frame that you can't think that way. Oda is the Picasso of pirate manga.
wonderfully detailed backgrounds. Every frame has them. Lots of manga write off backgrounds and just focus on stunning characters, but one piece gives you both. The backgrounds are simply amazing.
Character Art is off the charts. Every character has his own style too him. All of them are completely original and unique. Even the filler characters look good. One tiny flaw is that usually the female characters are somewhat bland in that they are all knockout babes, but I don't think Oda had much of a choice there given the market, and to be honest he does sneak a lot of ugly females in the back door on occasion.
Character 10/10
Character development is pretty much covered in story and is fantastic. They introduce a character and give them a back-story and continue developing them throughout the series. For instance, Nami's would be weather or not she can overcome what the fishmen did to her village. They never drag the story of one character on either. It's rather elegant.
Enjoyment 9/10
The early story was rather poorly done in comparison with the ladder of the story and you can see the mangaka improves with every chapter. So its hard to get into and like I said before 80-90% of people who haven't read One Piece is because they gave up early on without giving it a chance to improve. IT GETS BETTER!!!!
The action is more of a brawl then a strategy game which is a matter of taste really. Its actually rather easy for Oda not to screw up given the way he's done it.
Comedy is definitely there. Every character has their own quirks which never get old. At first glance they might seem like catchphrases but they are actually much deeper than that. They each have their own funny personality and quirks which play into how they interact with each other.
Overall 9/10
There's really no good way to score One Piece because early on they would rank probably a 7/10 or an 8/10 depending on how much the show suited your tastes, but with the show getting better every season its basically jumped a point every year. By now if I was to judge it just by the last year, I would give it a 15/10... IT GOT FRIGGEN GOOD!!!!
