This one is what hits me the most, because while I played Gen 1-4 games (sometimes it was just my friends/cousins lending me their DS for a while). It was Gen 5 that truly "clicked" with me. BW2 just feels like it was released yesterday honestly.
For me it's gen 6. I remember being shocked by mega evolution and the at the time new pokemon models. I remember waiting for ORAS to come out, same with sun and moon. The last games I was genuinely excited for were the ultra games, and despite me liking them at the time, those have aged terribly in my opinion, to the point I think USUM are the most overrated pokemon games.
What Gamefreak was able to do over the last decade:
*ULTRA CHANGES
I want to talk about the ultra games for a moment since I mentioned them above, and i haven't had and opportunity to do so. The reason I think they're so overrated is that, unlike for example, the switch games or something like diamond and pearl, which do get rightfully criticized all the time. Most of the "mainstream" pokemon fans praise them for some reason, despite their problems. I actually like the few changes they did implement like an extended pokedex and harder battles, but if you don't care too much about those aspects, the ultra games are pretty much identical to the base sun and moon.
I'm pretty sure you can get the SM outfits in the ultra games, and if you wear them, you literally couldn't tell the two sets of games apart.
The other changes are either things that no one seriously cares about like mantine surfing, the ultra wormhole minigame, and the myriad of straight lines they call new locations. And they straight up remove certain story elements like most of lillie's story, lusamine being turned into an anti-hero for some reason, and the post-game looker missions, no other "third version" removes content this way. Even if they didn't want to make a b2w2 style sequel, they could have added new locations, new regional forms, maybe even more megas, you know, things that would be worth buying this game for. If they could double the size of unova, a region based on a single city, they could have done this for a region based on an entire US state.
I also think they if they didn't want to change that much they could have leaned into the "alternative universe" theme the base sun and moon had and made usum take place in a completly different alola, maybe an alola with gyms, or had more characters with different personalities, similar to what they tried to do with lusamine.
And a lot of people like to pretend the ultra games don't have the same pitfalls as the switch games but in my opinion they do. A 2-3 hour long post game mission, linear gameplay with very little post game content and replayability, artificially increasing the playtime by adding in all possible legenderies (technically oras started this, but in oras at least the legenderies are in obscure locations like sea mawvile, or the one random cave on route 119, or through new features like mirage caves or souring). So the ultra games are pretty much about as long as base sun and moon. They simply just didn't add enough.
I unironically think Let's go pikachu and eevee, the games that came right after usum, are better games. Since lets go at least gives kanto a new look and feel, improved npc team, and added gym and elite 4 rematches and normalized them on the switch games.
Also the 10 minute long festival plaza tutorial is mandatory in the ultra games since you need visit the battle facility there for rainbow rocket, just why?!
Unlike SwSh, SV, or even something like XY or DP, the ultra games don't get the criticism they deserve, especially since these games were panned on release. I just searched up "pokemon usum bad" there's a single video talking about usum's problems, at least one that has more than 100k views, which is why i felt like talking about them here. Like i said, at the time i really enjoyed them, in fact there the only games I've ever had both version of, it's just I find them overrated for how little they added to sun and moon, and it's criminal they didn't make a b2w2 style sequel that continued the actually decently interesting story of sun and moon.
I know this is a very long post but I just really felt like talking about my issues with usum.
