Black and White I didn't like at all when they came out. The fact that you could only get Pokemon from Unova was (and still is honestly) a baffling decision that soured me on the whole thing back when it was announced even before the game proper came out, and I saw the story as more intrusive than interesting once I played it. Nowadays there was outrage when Sword and Shield removed the National Dex, and a lot of people think that the games are way too hand holdy and have way too many cutscenes, and I think that stuff was already present in some way all the way back in Gen V. Most importantly, the game came out at a point in my life where I wasn't really able to appreciate all the good things it did, and in general I was feeling pretty burned out on the franchise back then.
After a few years I did come back to the game, and I found it a delight. It aged really well in my eyes. A lot of it is thanks to its sequel, Black 2 and White 2, which unlike the first games I ended up loving almost instantly. Back when I thought I may be done with the franchise, those were the games that made me realize I still had a lot of love for it. Those games allowed me to engage with the Unova Pokemon in an environment where I felt I wasn't forced to use them, since they not only gave you access to every generation, they had the biggest variety of Pokemon seen yet in a main line game thus far back then. And because I was able to engage with the Gen V mons on my terms I realized I ended up loving a lot of them, and notice how good they fit in with the rest of the franchise's Pokemon, so I ended up really liking them.
The story also felt a lot less overbearing back then, in comparison to how Black and White had felt to me. Just one rival that showed up occasionally, most gym leaders had already been introduced back in Black and White so there was no need to go through introductions for each of them with a small plot line in the story, etc. So not only did I that allow me to enjoy the game much more on my own terms, it also allowed me to get interested and see the fascinating parts of the original game's story by paying attention to how the characters and region had evolved since then.
So when I did come back to Black and White years later, hoping to appreciate them more this time, I did so on much better terms, and I found a lot of stuff to like. The fact that I could only use Unova Pokemon didn't bother me anymore because I had grown to love them, and the characters and storylines became stuff that I found really interesting to see and analyze with the hindsight of the developments to come in the sequel, which allowed me to get invested into every character and plot point. I then played the Blaze Black and Volt White versions by Drayano, and that ended up making me like the games even more, now seeing them full of Pokemon from all regions. So overall, I really grew to love Black and White.
Ultra Sun and Ultra Moon had something similar happening. I first played them when they came out, right after Sun and Moon, because I thought that since they were making dual versions again, which had only previously happened with Black 2 and White 2, that the scope of these games would be similar, and since I had loved Black 2 and White 2 so much, I got Ultra Sun and Ultra Moon really quickly after Sun and Moon. Instead, I ended up basically playing through Sun and Moon again with slight differences, which made me feel really burnt out, and like Black and White, it caught me at a time in my life where I wasn't really able to focus on the good stuff so much as I was just looking to get through it.
Well I replayed Ultra Sun and Ultra Moon last year, and with the foresight of knowing the pacing of the game and the placement of the cutscenes and plot points, etc. I was able to focus on finding all the stuff about the game I liked. Things like the SOS Battles, Z-Moves, The Battle Royal, which I hadn't even tried the first time I played the game, and the general convenience of the region. When I first played Alola I really didn't like the layout, it felt way too simplistic, and the routes all felt like either hallways or open circles. Replaying it with that knowledge and trying to look for the good side I actually ended up liking all the streamlining, if nothing else because it made it feel like a unique experience on its own, and it allowed other parts of the region design, like the setpieces and the NPCs, to shine.
At the end of the day I think a lot of it is the mentality I come to these games with, and the point in my life I'm at. I hope I can find a bunch of stuff to love about Sword and Shield and Scarlet and Violet, as well.
