>>51072737for a marathoning purpose it'd be something like
1. DP: genuinely a good anime with an actual overarching plot, good characters, and Ash has a decent team and personality, and he's arguably at his smartest ever here with actual strategies applied in the battles
2. OG: it's the original so you know it's good and enjoyable. Falls off somewhat after the League and starts to become more typically formulaic, especially in Johto, but it has a good finale in the Silver Conference.
3. XY: it has really big highs, excellent animation with really good fights, again a good cast, the best villain team arc in the entire anime, but the fillers might not be your cup of tea and the infamous snub at the league finals might sour your overall experience in the end.
4. SM: comfy, fun, and quite different from what came before it. Animation either takes a nosedive for you or it stays about the same. I personally didn't like Ash in this, he's like a walking example of flanderization, and his team is pretty meh too. If you liked the way the anime was before this, none of the shit they do in SM might feel like it matters to you.
5. AG: It's sooo long and boring. Animation is actually pretty damn crap for what it is, no action even in fights that are supposed to be hype. Pretty much everything until Battle Frontier is a slog, after which it picks up somewhat but it's not enough to make it actually good. In my first marathoning, AG was the first time I took a break because it became too boring.
5. PM: bland, uninspired, made on a shoestring budget it seems. It makes a ton of promises that it never really delivers on, or do them in a way that feels half-assed. It had excellent potential but it's just squandered at every opportunity.
6. BW: pokémon anime at its worst. Worst Ash, worst cast, worst team, worst writing. Especially coming in from DP you will notice how much it shits the bed almost instantly. BW was the second time I had to take a break.