even though HGSS had no problem including all of Crystal's content.
While this was just a minor part of your post, this brings up an unpopular opinion of my own which I don't think I have ever posted before. Or multiple, depending on how you see it.
It annoys me when people give HG/SS praise for... well, a lot of things since I don't think they deserve most of the praise they get, but this one in particular. "HG/SS kept everything from Crystal." What did they keep exactly? The story parts were mostly minor and Eusine was there, but they decided to force you to go and catch Lugia/Ho-Oh unlike in the originals where it was optional (which I honestly prefered) while Suicune was left for the post-game (but it was at least not a roamer like in G/S, so that's good). Compared to Crystal, the way they did it in HG/SS just felt so unnatural and forced to me. While it has been ages since I last played Crystal, I want to remember that being forced to catch Suicune there felt much more natural than having to go after Ho-Oh or especially Lugia in the remakes which felt completely out of place. As for other things, they just copypasted the Platinum Battle Frontier and put it where Crystal had the Battle Tower, instead of doing something new and innovative like Crystal did. And one thing they actually didn't do was to keep the changes to the Pokémon distribution that Crystal did. Most of which was very good, and necessary. In HG/SS, some Johto Pokémon like Marill and Yanma are still mythological outside of swarms (which only start to happen during the post-game!) while others like Sneasel can't be found until after you have beaten Kanto. Someone tell me if I'm missing something but I can't think of any other notable changes Crystal made to G/S, only minor ones... and even so, I can barely remember any of these either.
And even if we give HG/SS credit for "keeping everything from Crystal"... so what? That doesn't excuse them from being awful games with lackluster content and some of the biggest gameplay flaws in the entire series. I'd much rather take OR/AS which admittedly might not have kept everything from Emerald (but once again, everything apart from the Battle Frontier are just minor things IMO). OR/AS do at least have really great gameplay and a decent amount of content which makes them miles better than HG/SS in my book. The same goes for FR/LG which are fun to play and they improve upon Kanto a lot, unlike HG/SS which didn't improve on Johto in any significant way.
Guess that's my new unpopular opinion for the day.
EDIT: Sorry, I must not be with it today and misreading things left and right
But I still feel it's a good rant about SM's story being better than USUM's so I'll keep it
-snip-
That's okay, mistakes happen.
I think you understood the original intent of my post, but just to make it completely clear: I think the story was better in S/M than in US/UM. I also found the Rotom Dex less annoying in S/M. But as for everything else, I thought US/UM were better than S/M, or at the very least equal to them.
I mostly agree with everything you wrote about the story. On the whole, I felt that US/UM made the story more complicated but not better. They didn't improve the story like Platinum and OR/AS did to their original stories, they made it worse instead. That said, there is one thing about the story I liked better in US/UM: some of the conclusions to what happened with the characters. I definitely prefer Lillie staying in Alola and becoming a trainer instead of traveling to Kanto, Lusamine not needing a cure (even if this meant we never got to see Motherbeast in US/UM, which is a shame) and Gladion going to Kanto and Johto to train and then returning. And even if I didn't think the story in US/UM was as good as the one in S/M, I still think it was fairly good on the whole. Far from the best, but about average or a little above when it comes to stories in Pokémon games.
I wouldn't go as far as saying it was a mistake, but implementation into other core games was very poorly handled. I don't get why Meltan doesn't have a normal evolution method, what's the point? Meltan stats are no more impressive then a basic Pokemon of a 3-stage family so there's no point in having it be a standalone Pokemon, it should evolve into Meltan (either at level 40 to reference the 400 candies originally needed or make it a trade holding Metal Coat or Magnet if they want to keep in-lore).
Unrelated to the above and below, but I totally agree with this.
Though I guess I could change the question to what about USUM was different that, if they wanted to, they would replay USUM over SM again. Because I'm trying to think (yes, the person who made two obvious reading mistakes today is now trying to deeply think, I know I probably should just quit while I'm behind) of differences between SM and USUM that'll make USUM better but to me they're essentially the same game.
I didn't explain this in my previous post because I didn't find it relevant enough, but I guess I'll do so now since you asked.
First of all, regarding the story. As said, I don't care
that much for the story in Pokémon games anymore. And that is actually because of S/M.
S/M does have a really great story, second best in the series after B/W if you ask me. But what about the rest of the games? There are massive issues. Let's take a look at what S/M had and didn't have.
No National Dex. Worst training spots since HG/SS. Post-game on the same level as X/Y (which is acceptable, but far from great). Worst Pokémon distribution since HG/SS. Unbalanced difficulty/level curve. They don't focus on showcasing the new Pokémon very well, they suffer hard from Johto syndrome. Massive fan pandering to Kanto/Gen 1. SOS mechanics (which I think are an awful feature, but that's subjective). Festival Plaza felt like a step down compared to the PSS, I also prefer Join Avenue as an actual Join Avenue as well as the Entralink for doing missions. It felt like they were gradually trying to remove Mega Evolution by making half of the Mega stones unavailable apart from Events (I like Mega Evolution, so that was a negative for me). No actual minigame. There are other things too, but I think those are the biggest issues I have with S/M.
Does that mean I hate S/M? No, I actually think they are good games despite their flaws. The also have several positive points. Apart from the story, I liked the Alola Pokémon, the Battle Tree, Poké Pelago, Pokémon Refresh and Z-moves, to name some things.
What am I even trying to say here? That for me, it felt like S/M focused so much on the story that they forgot about the rest of the games. Compare this to the two previous first pairs:
X/Y did indeed have a bad story. But they have so much else which I think is more important than story. Epic training spots, a National Dex, the PSS, Battle Maison and Pokémon Amie. They were also way better in terms of the regional dex, Pokémon distribution and focus on the Kalos Pokémon. That's not to say that I think X/Y are flawless, but I definitely prefer them over S/M because they do more right when it comes to the things I think are the most important in Pokémon games. In terms of raw gameplay, I think X/Y are among the best in the series, while S/M are quite a bit lower.
Then there's of course B/W which has the best of both worlds: best story in the series AND great gameplay with great training spots, great post-game, good Pokémon distribution with complete focus on the new Pokémon, fun minigames and great Battle Facilities.
Looking back, I guess I was also a bit disappointed in S/M since I had way too high expectations on them, they weren't the games
I wanted them to be. I had too high and wrong expectations on them, which made me a bit disappointed when I first played them.
But now I got carried away, the question was why I prefer US/UM over S/M. I guess the simple reason is that I think US/UM are better when it comes to the things I look for in a Pokémon game. Story is not one of them. Or rather, it is no longer one of them.
Kurona already mentioned some things: Regional Dex expansion and slightly better Pokémon distribution, Move Tutors, Mantine Surfing, better graphics and interfaces (even if the graphical changes are mostly minor).
There are other things too such as the Battle Agency, 5 completely new Pokémon, new Z-moves, Rotom-Powers, so many legendaries to catch and slightly better training spots. You can also get ALL Mega Stones in the games without events. US/UM also feel faster than S/M to me. The difference isn't as big as say, D/P and Platinum, but if you go back and play S/M after playing US/UM, it is definitely noticable. I never cared much for the Rainbow Rocket part though, it could have been handled better (but I consider it as "story", so technically I have already gone over it). I prefered the Looker story in S/M, the negative being that you only have a limited number of UBs to catch there while US/UM gives you an infinte amount. There are also things that already existed in S/M that I liked which were kept in US/UM like the Battle Tree, Poké Pelago and Pokémon Refresh.
Basically, US/UM offered more when it comes things that matter to me in Pokémon games. While many of the improvements are minor, they are enough to make a difference. I guess I'm contradicting myself a bit here since I previously complained about Crystal and Emerald mostly only having minor improvements, so I want to clarify that I do prefer Crystal and Emerald over G/S and R/S, but I am annoyed when people bring up their minor changes for their remakes since I didn't find it to make that much of a difference there.
With all of this said, US/UM could definitely have done more. Having even better training spots and a National Dex would have made a lot more for me. Some things could also have been executed better such as the Ultra Wormhole ride minigame. They should also have gotten rid of the SOS mechanics and not have made the Rotom Dex start babbling endlessly.
On the whole, I prefer US/UM because as I have said (it will be the third time now, I think) they do more when it comes to the things I care the most for in Pokémon games. However, I did ironically enough find US/UM mostly boring to play through when it came to the main game. I think this was because of many different factors. First of all, they were released too soon after S/M, and they were too similar to them. It also happened when I was going through some changes in my life and had less free time to play compared to when I played S/M, which made it feel slower and like I wasn't making progress as quickly as I should have. But if I were given the choice of a new game to play today, I'd definitely pick US/UM over S/M. And I really enjoyed the post-game of US/UM, I'd even say it is the third best in the series on the whole. That definitely made up for the main game feeling boring to me.
I hope I managed to explain how I feel here. On the whole, I really like US/UM in the end. They are my third favorite main series games released for the 3DS, and my fifth favorite games in the series on the whole. Gen 7 is my third favorite generation, and that's mainly because of US/UM, not because of S/M. I'm sorry if this post is messy and unstructured, I didn't really have as much time as I wanted to get all this written and I have probably forgotten some things, but that's how it will have to be. At least for now.
Lastly, on the subject that appeared afterwards regarding some Gen 1 mechanics. I agree about Mimic, I always liked how it worked in Gen 1. A potentially unpopular opinion is that I also liked how Roar and Whirlwind worked in Gen 1, as they had no effect in trainer battles. Status being partly related to type was also cool. I disagree on Hyper Beam and Rage though, and Disable should not be changed from how it works now.