I'm somewhere around 350 episodes I think. My least favorite would be the episodes with a lot of screaming. I know it's Anime and a bit of that is expected but some get to a whole new level.
The anime has been in production so long it's extremely hit or miss, depending on where in the show's run you look. The effort put into the production falls of a cliff several times. It's part of the reason I personally can't stand it in comparison to other anime series or even the manga.
It's a pity, some of the OP movies are excellently produced and I'd really like it if a version of the whole story with FMAB level production quality existed. But that'd be a massive undertaking at this point, so it is unlikely to happen.
The episodes airing currently have pulled their shit together on the animation, but they are still re-cycling the same old OST recordings and SFX samples, making the anime unwatchable for me.
Kinda, but if the Simpsons was always a good show and the production quality just sucked sometimes. The One Piece anime isn't pulling new shit some new writer came up with unless it's doing a filler arc. For the actual story, Eichiiro Oda, the mangaka, has always been in charge and is still writing and drawing straight fire.