@Nuzzie:
Also this thread is chock full of ["bad"] taste
Thirded, or whatever number it's at now.
And so, to share my view:
Everything up until somewhere in Skypiea is gold (filler removed). Paying attention to all the details is astounding. I watched the show first, but ended up reading later, though they both contain the same essence I'm speaking of… given enough patience. (I had a lot of that back then.)
I know that reading weekly can certainly put a strain on things, so take this as "knowledge" from someone who had never heard of filler/shounen/jump, nor even experienced any shounen, before starting the series. (Also, I've gone through most of the series several times).
There's so much good stuff, within the arcs people think are crap, that there's no point in explaining; just go experience it all again and see for yourself. (I prefer the anime 'cuz it aides in this philosophy more appropriately, especially since its quality is mostly high). But the main thing that sticks out in my mind is how inter-woven the events are in the time between Laboon-Arabasta's End. If anything requires the word "epic" to describe it, this is it; and there's nothing even flashy about it!
From Skypiea on out, things start getting out of focus. Though personally, I don't care how pissed off I get at any arcs, after the first dozen, for being more of the same or what have you. (I agree; Oda set the bar WAY too high. Yet amazingly he still matches it half the time.)
So, if I had to pick one arc, it would be Enies Lobby; however, that began as I started weekly watching, which may just prove my point that the best way to experience this is to ignore the series and avoid the anime (for now?) in order to take in its whole future simultaneously–-but good luck evading addiction to achieve that! Plus, everyone's reading it weekly now, but that don't mean future sittings can occur.
Everything has a purpose (a lot of the time). It is for this reason that I can't stand people complaining about individual chapters, or especially individual arcs that are actually good overall (like the Kuro arc). It's like they don't even know why they're reading motherfuckin' One Piece.