Japan's attitude towards third versions and remakes is very, very different from the West's attitude on such a matter, and Japan is much less nostalgia driven in their opinions than the West. Generally, third versions and remakes are viewed in a much less favorable light because people in Japan have a "purist", for lack of better word, mentality towards works and prefer the original work as it is. Meaning they essentially prefer a one and done situation when it comes to works: the original work in their minds is best left as is. Since Diamond and Pearl is, by all means, the original work and Platinum is essentially a revision of it, they hold DP in higher regard and Platinum is overshadowed since it was essentially a revisit of a work that was already made, and also why HGSS is ranked fairly low. BW2 is the only other "region revisit" to have made it, and is more popular than HGSS and Platinum, likely because it is an original work in its own right being a sequel story to BW1 and a unique experience in and of itself.
With that in mind, it makes me wonder if Legends: Arceus will be much more warmly received amongst Japanese players than past region revisits like ORAS, FRLG, and even HGSS.
That being said, it's a real testament to how excellent Platinum and HGSS are when they are the only respective upper version and remake to even make it into the Top 100 games of this poll at all. When it comes to third versions, none of Emerald, Crystal, or USUM made it in whatsoever, and none of the other remakes except HGSS made it, a true testament to the greatness of Platinum and HGSS.
Also I am extremely glad to see Gen 5 getting the love it deserves, with BW1 making it into the Top 30 and the 4th most popular Pokemon game in that poll (only behind DP, SwSh, and RB), and BW2 making it in 60th place. Gen 4 and Gen 5 taking all the wins here, with DP taking the lead, Platinum and HGSS being the only upper version and remake to make it into the Top 100 at all, and both Gen 5 games taking solid spots in the rankings. DS Era Pokemon WINS!!!!
Other than that, Red and Blue seem to hold a comfortable third place amongst the games and a solid 24th place (or shall I say, Red and Green since this is Japan we're talking about). As the original games of the series it's no surprise that they are still iconic to this very day. I'm kind of surprised to see Sword and Shield so high though, even speaking as someone who unironically loves that game and considers it the most fun I've had playing Pokemon in years, I'd think that given how divisive and controversial it is it would not even be close to being that high in the rankings. I suppose people in Japan were ultimately a lot warmer towards SwSh overall? Maybe the DLC really upped many peoples' impressions of the game in the end? Who knows? That sure is funny to see that game make it so high though. Or maybe Sword and Shield's merits were things the Japanese playerbase valued so much that many ended up loving it in the end? That really sticks out, and I say this as someone who really liked SwSh.
Very funny to see Sun and Moon and USUM not make it into the Top 100 at all. Poor Gen 7 seems to be the major underdog of the franchise right now as is, at least amongst the Japanese playerbase.