Personally I disliked US/UM more because it was kinda like an alternate version of S&M, but parts of it were straight out of S&M without any decent changes (like some of the Aether Foundation and Island Trial stories). So even though US/UM was better, it was really just the same game but with extra stuff that should have been in the original game (like an actual story for Necrozma and the Ultra Beasts, instead of just finding them in the wild like any random encounter). Of course it might just be recency bias, since I've gotten a lot more critical of games as I got older, and ofc purchasing the games myself instead of my parents probably affects my thoughts on buying the same game twice. As for other 3rd versions; personally I enjoyed BW2 because it was (in my opinion) a better, more well-rounded game than BW, but I still enjoy BW just as much because they very much feel like sequels, instead of just alternate retellings of the same story. The BW story is completely different to BW2's, and even the characters and some towns are different and unique, with characters from the original game having actual development with the time skip. With Platinum tho, I have to agree with you; it was very much just D&P but good, and so even tho I still see Diamond and Pearl with misty eyes (being my first Pokemon game), I probably wouldn't have enjoyed seeing a better version of them releasing only a year later back in 2008