Note: Before you read this, I must inform that I read all episodes in Japanese, so I do not know the official English spellings, and I may make grammatical errors, as English is not my first language.
I been talking with my other Japanese friends and we all seem to agree to the fact that Arabasta Ark was the peak of ONE PIECE and Oda has not been as good as he has been since then. We feel that certain elements, such as complexity, dept, and entrainment of stories is lacking in the current stories. Though, Skypiea is comparable to the Arabasta Ark, but still not as good. Some claim that this is because we were middle schoolers during the Arabasta Ark, and now that we are college students, we don’t get as excited as we used to do with the current stories. Don't get this in wrong way, we all have been One Piece fans since episode one and we all still rate ONE PIECE as number one manga.
What does this all gibberish mean? Well, if we look at the Arabasta ark closely, we have the main story of BW and Croko trying to take over the Arabasta (for Pluton of course). The whole story starts when Luffy and co. meet the Giant Whale and Miss Wed (Princess Bibi) at the Futagotou. From this point to end of the Arabasta Ark, there are several “unrelated” but important topic/themes covered and at the same times the Mugiwara Pirates were able to travel to several different islands; thus the word complexity and dept. These include the whale, the two Giants at the Little Garden, the Goldfish (Ussop’s earlier story), Choopa’s story at the Drum Island, Black beard/Ace, and finally Pluton/Ponegraph.
We also believe entertainment (comedy) aspects used to be very balanced as they were added when necessary but not to the point were flow of the story was destroyed. Now it seems like Oda is rushing through the story a little and there are some “moments” of nice stories but the comedy became the main part of the story.