All right, using bdt's tier list as a guide, here is a roughish guide to how I view the main series (and LGPE, since it was there) games. Other spin-offs like PMD are not on here, but I'm not going to bother to add them and figure out where they are placed. Just know that games like PMD2 would definitely rank higher than at least some of my B tier, if not some in A (maybe some S as well? Really don't know here.). Without further ado, let's cover all the basic entries in this list, shall we?
S (Amazing) tier:
HGSS: Yes, they have some problems. Yes, they didn't fix enough issues. But still, at the end of the day, I don't care too much. Wonderful remakes, wonderful aesthetics, lots of content, nice added things/features/places/etc., some actual fixes to the OGs, etc. Just the best of the best, overall.
Platinum: Platinum fixes up DP and makes a game that is truly nice and holds up pretty well. The game has an actual semblance of difficulty, which is something you just don't get these days in this series. There's plenty of of content, ensuring you'll have things to do to extend your playtime/value of the game. The aesthetics, while not as good as HGSS's or some others', are still nice. All in all, just another amazing entry in the franchise and definitely going to stay the definitive Sinnoh experience.
BW2: These games far out do their predecessors in my opinion. There's more to do in them than the story, which is nice. There's a f*ckton of features and content (seems to be sticking point for me, no?), more than probably any other main series game, which is a nice feat. They somewhat fix the lacking aesthetics of BW1, another thing I appreciate. They're also the least cynical "extra games in a Gen that aren't a remake" games in the series, being actual sequels instead of just another "enhanced" version. While these games aren't good as the aforementioned S tiers, they're still amazing.
A (Great) tier:
Emerald: Expands on RS in a very nice way. Some people might dislike fighting both Aqua and Magma, but for me it's like,"I like fighting villainous teams... bring it on!". Increases the difficulty of the OGs, something which is always nice. The Battle Frontier is a neat addition and the other expanded content is always appreciated. Combine this with the nice aesthetics of Gen 3 Hoenn and you've a nice game. And the definitive version of Hoenn.
Crystal: Gen 2 is where I landed into this series. I started with Gold, but Crystal is just "GS, but better". I'm a nostalgia driven man it seems, and these games of course hit the spot. Nice aesthetics, nice graphics/sprites, nice music, content, and more.... these games have quite a bit. Add in Crystal's expanded content, and well, you've a nice game.
GS: Already covered most of them in the Crystal entry. It's just that they're not Crystal, so yeah.
B (Good/Solid) Tier:
DP: I don't remember hating these games like others here. Sure, they're slow, have an over reliance on HMs, have a sh*t regional Dex, and more, but still. The Sinnoh region is expansive and has lots to do, even in these games. Plus, these are the games that introduced the physical/special split, one of of the best changes in the franchise, bar none. As stated numerous times in the past, these games are just rendered obsolete by Platinum.
FRLG: Honestly, I don't know whether I prefer these games or RS. I guess these games should rank higher though for not being rendered obsolete by a later game, if anything. Anyways, FRLG are pure and uncomplicated games: they're just solid all around games and not bad remakes. They just don't do enough to "wow". But don't let that be too much of a knock on them. Add the expanded content and I'd call this the definitive version of Kanto (for most players).
RS: Not much to be said here. Solid games, nice aesthetics, etc. Just outdone by Emerald.
RB: The OG of the OG. The ur Pokemon games. These games might be old, poorly designed, and buggy, but I can't help but get some endearment and wonder from them. They really are a trip to the past. And while they're jank, they're a sort of fun kind of jank, you know? And the buggy mess helps their charm as well. Definitely beaten out by all the previous entries in this post, but I don't hate them and they definitely have a sort of nostalgia to them.
Yellow: With better sprites, graphics, boss teams, etc. you'd think this game should beat out RB, right? I dunno, they're basically equivalent, but Pikachu, (wo)man.
C (Average) Tier:
BW1: Most people here seem to adore these games... I'm not one of them. These games really where my unquestioned liking of Pokemon started to wane. And these games really did seem to take it from from high to low quickly, with just themselves. I remember being hyped for these games, but when they came out, I just didn't feel it. Coming from the highs and content richness of Platinum and HGSS to BW1, where all there is is the story, and well, you get disappointment. They also just lack aesthetically. Not even a replay years later could change my opinion much. They're definitely not bad games, but they just don't click with me. One of two games that taught me to not blind hype for things.
E (Bad) tier:
(Yeah, we skipped D. These next games are so bad in comparison to the previous entries that they need the skip.)
USUM: USUM and me are complicated. On one hand, I made a hard mode hack for UM. On the other hand, these games are just bad. The typical modern Pokemon BS, with long, poorly written, unskippable cutscenes every two seconds; poor world design; tons of broken ass mechanics; dumbing down of the game; etc. You name it. And USUM has the problem of being the most cynical of "enhanced" versions by far, being obvious bait. In USUM's defense over the next entries, it has more content and difficulty. And I made a hack for UM. And I prefer Gen 7 slightly to 6, so yeah. Stockholm Syndrome is a bitch.
SM: Take USUM, remove content and some difficulty, but improve the writing and story, and you've got SM. Not much else to say here, barring that adding Hyper Training was long overdue.
ORAS: These games are just laughable in comparison to the OGs. Aesthetically, they look much worse (really not a fan of Gen 6's aesthetics). They take the already not very high difficulty of RS and make it far easier, with the usual busted ass mechanics. Sure they add some content, but Emerald did it better, and without insulting my intelligence. Really, these games are forgettable and thoroughly beaten out by what came before. Only strength they have at the end of the day is the P/S split.
F (Fail) tier:
XY: Remember how the E tier games where bad? Well, these games manage to be even worse, somehow. They look and play bad, have some of the most lifeless writing I've ever seen, are piss easy, started the introduction of most of the busted ass mechanics I mentioned, and more. These games physically and mentally hurt me to play, something I cannot say for all the previous entries on this list. Yes, they've some good points, like finally making getting competitively viable Mons not such a pain in the ass to get, but it pales in comparison to the bad.
G (Garbage) tier:
(I have not played the games in this tier.... but do not plan to anytime soon.)
LGPE: Easily the worst rendition of Kanto. Extreme dumbing down of the games with gimmicky Pokemon GO capture mechanics. A giant meme.
Sw(i)Sh: These games really are the straws that broke the camel's back for me. XY began the strain in earnest, but ooh boy, these games took any Stockholm Syndrome I had for modern Pokemon and broke it. Pathetically easy, outrageous removal of content, nothing to do, Movexit, Dexit, more busted ass mechanics, etc.... I could go on. They didn't do the "enhanced" version this time and added Nature Mints and stuff, I guess.... but meh. Those won't have me play these piles of excrement.
So yeah, that's a rough tier list... with all the good and the bad.
