My favorite games are B/W and B2/W2, followed by X/Y and OR/AS.
Least favorite things about:
B/W and B2/W2
- I was never a huge fan of the way diving worked in these games. It was limited to just one area, there were no wild Pokémon to encounter while diving, and there was a step limit, meaning you could never explore the entire area in one trip there. It also required other HMs to explore the entire area, and it seems like you can't reach the second floor if you take too many steps on the first floor. For these reasons, I didn't get around to explore the Abyssal ruins in my Gen 5 games until 2015. That said, it was sort of okay in the end. I used an external map while exploring it and marked all the items I had found, making it feel like a treasure hunt. And after replaying R/S/E and playing OR/AS, diving isn't
that great in those games either. It is better than in Gen 5 for sure, but far from perfect. I think the idea of diving to the Abyssal Ruins in Gen 5 and exploring that area was a cool concept, but the execution should have been better.
- Many others have complained about the Key System and that Easy/Challenge Mode is post-game only. I partly agree, but I think another issue is that the Key System (apart from Memory Link) could only be used through local wireless. It would have been better if it had been possible to use it through both local wireless and Wi-Fi, this would have given more players a chance to utilize it.
- Not really something about the games, but about the circumstances surrounding them. The closing of Dream World and Wi-Fi. I really liked Dream World, and having access to Wi-Fi was great too (I used online a lot in Gen 5, much more than in Gen 4), so it is sad that it no longer exists. I understand why it had to be shut down, but it is still a negative.
X/Y
- The lack of content. These games have amazing gameplay but sadly not that much to do. In terms of content and post-game for first pairs, they are a step down from the greatness of B/W and D/P (but they are at least better than R/B, G/S and R/S). What they do have is mostly really fun and well executed though, so that's good.
- Bad story/characters/lore. A pretty big step down from the greatness of Gen 5, though it was still not the worst in the series. But story isn't super important to me, and I thought the post-game Looker Missions were great.
- The lowest amount of new Pokémon to date. Previous generations (especially Gen 5) had both quality and quantity, but Gen 6 had only quality.
OR/AS
- A small regional dex compared to B2/W2 and the other 3DS games. There were also a few types that were underrepresented, such as Ghost, Ice and Fairy.
- Too much water, not enough variation. The water routes and areas should have been more varied when it comes to wild Pokémon and environments. Now most of them look and feel the same and have the same Pokémon on them. The DexNav exclusives help a little but not that much, sadly. And they only start to appear after you have beaten the Cave of Origin.
- These games were not that impressive in terms of new features and content (but again, they are remakes, so what else should I have expected?). Most of the content and features they have to offer already existed in either R/S/E or X/Y, there were a few new things such as the DexNav, but not that many.
My least favorite games are HG/SS. Apart from them, I guess there's also R/B/Y and G/S/C? Though I'd feel wrong for being too negative towards them. That said, I'd rank R/B and Crystal higher than Yellow and G/S, so I'll do the latter two as well.
Favorite things about:
HG/SS
- The Dowsing Machine. By far the best feature of these games, and one of the few good ones. It was amazingly useful, I always used it to look for items while playing these games. Second best one in the series on the whole.
- The breeding improvements. In theory, at least. Traditional breeding for IVs is easier than in D/P/P since the Power Items now pass down IVs, and Male Pokémon can now pass down their Nature as well. RNG breeding is also said to be easier than in D/P/P. I can't really do a fair comparison here though since I have never done any traditional breeding for IVs in HG/SS, nor any RNG breeding in D/P/P. But I'll still stand for it based on theory and what other players have said.
- Many legendaries to catch. This is something I always like, no matter the games. HG/SS are the third best in the series along with Platinum and B2/W2, so that's really good.
- The ability to mark things on the Town Map. I found it very useful to use as a reminder if there was something I wanted to do/explore on a route later but didn't have the ability to do so on my first visit.
Yellow
- Better front sprites than R/B.
- The ability to get all starters during the main game, without trade or doing anything special.
- Like all third versions, Yellow did some very fun and interesting changes to the Pokémon distribution.
- While I didn't like Yellow as much as R/B, I still thought it was pretty fun. I had a lot of fun with it back in the day when it was new.
G/S
- They improved upon R/B/Y in terms of graphics and game mechanics, they also had a way better bag and PC system (the latter was still far from perfect, but an improvement nonetheless).
- They added several new features that became standards in the series, such as breeding, hold items, genders, a time system and shinies.
- The Johto Pokémon.
- These games do (along with Crystal) give a certain feeling of mystery which I never felt that the remakes managed to give me. That was actually really cool now that I think back to it (this might just be nostalgia speaking though).
- Same as with Yellow; while I didn't like G/S as much as Crystal, they were still fun to play and good for their time at least.
Move Tutors based on Shards was a good idea (introduced in Platinum, I think?), but actually obtaining the Shards was a fairly tedious affair.
Don't know if you are aware, but there is a Funfest Mission named "Find Shards" which is self-explanatory as it let's you find large amounts of Shards very easily. I always used it to find Shards and I always had a ton of Shards in B2/W2. It is only available after beating the main story though, so it doesn't really help that much during the main game.