The problem here is that you take into account a Glalie that only shined with Pokémon whose level cannot be determined, such as charizard and a sceptile. We don't know if Sawyer's and Alain's Pokémon are stronger than the Pokémon Glalie defeated and that's why they couldn't win. (Bisharp, Slurpuff, Salamence)
I mean, Sawyer was a rookie. He was getting beaten fairly easily by everyone when we first meet him. Of course, he experienced Cameronian levels of ludicrous power up with his final team, but regardless, he's not some highly experienced trainer. Glalie defeated Clark's Charizard (type-disadvantage), Katie's (a clearly skilled trainer) Dugtrio and Misdreavus (only losing to Destiny Bond), Morrison's main Pokemon in Metang, and lastly drew against Tyson's strong Sceptile. Regarding the latter, both Pokemon were obviously quite powerful, judging by how insane was that explosion of Ice Beam and Solar Beam. None of these trainers were shown to be incompetent, and they battled with skill and firepower. As Brock said, the Hoenn League had "some of the greatest battles [he'd] ever seen," so these weren't low-level matches.
The same issue also holds true for the Alola team. In fact, as I've seen others in PAD argue, some contest that the Manalo Conference and Kukui weren't the same pedigree of opponents whom Ash had faced at prior leagues. Don't get me wrong, I'm not even agreeing with this take at all, but my point is this same argument also works against the Alola team, regarding the indeterminate levels. What we do know though is that the Hoenn team barely lost to the winner of the most rigorous format league conference ever, and they got even better in the Battle Frontier competing against the Frontier Brains (who are supposed to be close to/on par with the Elite 4).
You also take into account a Corpish that after beating Swampert, loses against a Chansey... It doesn't help that he probably can't beat Politoad in the next few episodes.
That Nurse Joy was an ex-Trainer and obsessed with battles. Corphish is allowed to have losses too. It can have good and bad days, and its peak performance was tanking and winning aginst Frontier Brain Tucker's Swampert and Arcanine alongside Swellow.
Melmetal defeated Empoleon, but lost to Silvally and Incineroar. Moreover, it's not as if in those battles Melmetal showed immense tanking ability or power.
We also don't know if Kukui's Incineroar is stronger than Darkrai then Incineroar>Sceptile. People overrate Sceptile sometimes. Darkrai only wins cause dark void, he's not even level Ace E4
Why is Darkrai "barely/not even Ace E4"? Legendaries are treated in the anime as anywhere from being barely beatable to virtually unstoppable. Darkrai was undefeated in all of Sinnoh. Latios was arguably even more powerful, as it took out Sceptile, who was damaged but still had something left in the tank given how he looked, and easily KO'd Swellow, one of Ash's toughest and tankiest Pokemon ever.
Tobias is such an unknown trainer. We don't know if he had four even stronger legendaries. We don't know if he went ahead and battled the Sinnoh Elite 4 and Cynthia, and even if he did, whether he left and went on to go catch more legendaries. He's the literal anti-DEM, a Player Character with likely six legendaries solely created to stop Ash from winning the Sinnoh League.
Flint's infernape (Buizel, Infernape, Pikachu destroyed ) did more than Tobias's Darkrai (Torkoal, Heracross, Gibble and it was damaged)
I'm confused by this take. Is this supposed to be reasoning for why Darkrai is "barely/not even Ace E4?"
Pikachu is known to have highs-and-lows, with a very low floor due to him being a measly Pikachu species, and an unlimited ceiling. Pikachu pretty much always has his greatest performance in the final battle of a series, but usually isn't as good before then. So while Pikachu did hold off for quite a while against Flint's Infernape, I doubt he was anywhere close to his end-of-region peak form. Keep in mind, this was during the OS-DP era, where the Elite 4 and Champions were pretty much nigh unstoppable.
Ash sent out an anti-Darkrai composition: Torkoal and Sceptile battled legendaries before, Heracross had type-effectiveness against it, and Gible was an unorthodox trump card due to its wonky battling style, size, and the fact that it can use Draco Meteor.
Knowing that Darkrai is barely Ace E4, it can be inferred that Ash-Greninja could beat Sceptile and some other AG Ash Pokémon. Even so Hoenn Team would win but assuming Torkoal and Glalie can with Goodra and Noivern which seems unlikely to me (You can use the example of Registeel vs Torkoal, but still Noivern defended better against Zapdos)
Wait, are we debating Hoenn vs Alola, or Hoenn vs Kalos? I mean, I genuinely think the Hoenn team,
especially with access to gimmicks, can beat the Kalos team, and you seem to agree with me?
I haven't stated anywhere that Sceptile defeats Ash-Greninja BTW. However, even if Ash-Greninja does win, it's certainly not going to be a stomp, and the other chip damage that Ash-Greninja would receive from the other Hoenn Pokemon ultimately brings him down.
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At the end of the day though, it all comes down to plot and narrative. The writers could have Palpitoad OHKO Corphish next week, even if it won't make any sense. They could say the BW team beat the AG team in a practice full battle, and that's that, even if it makes no sense.
Even if the Hoenn team ended up with a higher aggregate average team ranking based on how their individual members rank among Ash's "tier lists", it's the Kanto Gang of Four that defeated Brandon, the Sinnoh team that defeated Paul, the Kalos team that reached the league conference finals, the Alola team that made Ash the Champion, and the Journeys team that made him the #1 in the world. This is why people underrate the Hoenn team so much.