doing huge rereading marathon to get back to this series, didn't done good to this arc.
even though the ending was epic, it wasn't without any ridiculous trouts, herm, ruby/sapphire/emerald/silver learns the "secret moves" so fast? pikachu group learns volt tackle just like that? and that's not everything. the end was clearly rushed, but even so, i glad it did, because this arc was the weakest. and emerald as a character even at the end hasn't grow on me even a bit. the reunion of 10 pokedex holders was cool, but clearly it was a lot for the author to handle, so he chose to concentrate mostly on the 5 main character of this arc (crystal, gold, ruby, sapphire, emerald). and he didn't even bothered with giving us a little taste of that huge tournament, but chose to focus on crystal/oak, why is that?
in other words, this arc was the first the felt truly a mess. awful pacing over the arc, too much expedition on the battle facilities that drown away the less careful way battling was in this manga so far, weak frontier brain characters - in this area, i can say that even the anime made better way, and the final battle ,while feeling epic ,comparing to previous arcs felt the weakest, mainly because it overused only one villain with huge water monster without any imagination.
i wouldn't call this arc a "filler", but considering it was done only in favor of ending the FRLG saga, it might be true.