>>50976734GSC: This is, and probably always will be, my favourite arc in the series. The motivation and methods of the main antagonist are objectively retarded, which I could clearly recognize as a kid, but even in spite of that I still love it. I love the main characters (Gold is super based, and I've always had a soft spot for Silver), the main characters of the Gen 1 arcs show up as well and interact with the new characters, and the final battle against the antagonist is pretty cool. Another point against it is that the flow of the story is interrupted to introduce Crystal (Pokemon Crystal came out after the arc was already being written), and the art changes with the introduction of Crystal as well (Mato's art was pure sovl, Yamamoto is ok but has been on the decline), but I think it's worth sticking out to the end for the resolution.
RS: When I read this as a kid I remember not liking it that much (I thought Ruby was annoying), but re-reading it made me appreciate it a lot (Ruby is still annoying, but likeable and charming). It was planned out extremely well, from the interactions between the two main characters to the events around the box legendaries, and it was impressive how the author was able to maintain the tension near the end of the part for quite a while. I have one criticism which is a major spoiler so I won't say it here, any other criticisms I have are just minor nitpicks.