Now THIS is more like it! Chemical Plant is one of the single best zones of any sonic game; they absolutely nail the pure speed and adrenaline that comes with it. The other stages are a little bit hit or miss but overall I enjoy them all for playing very differently to each other.
My only criticism would be that boss fights, particularly the final zone, are not particularly enjoyable. Sonic has struggled with these as early as his first appearance and while I like that some of these have very quick ways to beat them, none are particularly interesting. The final egg robot is a pain in the ass as every time you die you have to fight mecha sonic AGAIN! And I died a lot because of his tiny hit box.
Other than that, they nailed the blue blur on their 2nd attempt. Good job.

(This is a review for both games)
In theory, this game is the perfect 2D sonic: excellent soundtrack, a well-told but not intrusive story, inventive and speedy levels... well, for the most part.
Unfortunately, it's a case of quite a few tiny cracks in its hull that bring this ship down a little bit. Every level seems to have some obtuse gimmick that has no right to be in a sonic game (the spinning wheels of Marble Garden, the infinite pits of Ice Capp, tedious seesaws in Mushroom hill, too many aspects of Sandopolis to count, instant death crushers in Flying battery and who could forget the barrels of doom).
If none were there, I would absolutely say this is the greatest 2D Sonic. But they are. So it's not.

Also quick one about the MJ/Jetzons original soundtrack. I definitely prefer Icecap, launch base I could go either way but the original carnival night track is genuinely awful for a Sonic. It has no driving rhythm; in fact, there are tons of long awkward stops, a but like the actual level. Also, using the Entry of the Gladiators melody in your circus-themed composition is just creatively bankrupt. I know music is about personal taste but I think this track is horribly overrated still.

Sonic CD is not a well-designed game. It is cryptic, confusing and Wacky Workbench can go fuck itself. This is what I thought to myself on my first playthrough.
However, I find this game so incredibly endearing like no other entry in the franchise. As a result, I have found myself coming back time and time again, working around the bullshit to revel in 2 specific aspects of the game that are undeniably brilliant.
The first is it's soundtrack. Having a past/present/Gfuture/Bfuture of a stage is not only an incredible concept visually, but also a composer's dream. As if that weren't enough, SEGA of America heard it and thought "we can do better than that." It's still disputed if they actually did (the boss theme haunts my dreams) but having two entirely distinct and inspired soundtracks in any game is never a bad thing.
The Soundtrack is a big part of the other thing that gives this game its gravitational pull, its psychedelic atmosphere. Some do not enjoy the flashing lights and vibrant patterns/colours of it's alliteratively named stages, which sound more like intense cerebral notions rather than geographical locations. I for one can tell they were on something when they made this game, and I want their dealers number.
Not a good game, but it was never really trying to be one.

For a first attempt by DIMPS, pretty solid.
There's a few things I outright hate: screen size is always going to be an issue. Bosses suck, so it's not just SEGA that can't make a decent sonic boss. I like the unique themes of every level a lot, but they are all varying degrees of frustration. Finally, the special stages are entirely broken and practically unbeatable. What's worse is if you fail, which you will, that's it. No retries until the next playthrough.
I will say this game's sprites look fantastic, Amy as a character is always a fun challenge, and I have no idea how they crammed some nice songs into the archaic GBA sound chip.
Frustrating. But a good sign of what's to come from DIMPS

I have one glaring criticism of this game that I want to get out of the way before I praise the shit out of it.
The worst boss fights of maybe any game I have played in recent memory. They are horrendously long with 8 hits and death means starting all over again. They are the only thing that stops me coming back to this game and completing 100%, which is a damn shame...

Anyway, Sonic Rush is fucking phenomenal. I've never quite understood how boosting is a problem in Sonic, as long as I'm going fast I'm having fun. The point is while you have the option of going at max speed all the time, you'll be met with death if you do it willy-nilly about 50% of the time. Once you realise that, it's infinitely more enjoyable. The soundtrack and every aspect of sound design make me feel as if I'm playing an arcade racing game of the early 2000s. It's so uniquely creative, thanks to its Jet Set Radio Composer, and it fits this game absolutely perfectly. Even the final boss is redeemed by its adrenaline-pumping beat and Blaze even gets remixed music for every stage. S ranking stages in this game is ludicrously challenging due to the trick system and going for them changes how you play the game entirely. It's about more than just going fast, now you have to go fast AND look cool!

If you can get past its woeful bosses (good luck with that) this is an exceptional sonic game. I'm going to go listen to the soundtrack for the millionth time.

Undeniably janky, but in all the best possible ways. Some of these Sonic stages (Emerald Coast, Windy Valley and, objectively, the best Speed Highway) are still unrivalled to this day in their speedrunner-friendly level design. I know stuff like the cutscenes/voice acting and the generally unstable nature of pretty much everything can put people off, but I love all that stuff! It's a certain humour of poorly made early 3d models that just can't exist anymore. Of course, there are the bad janky parts, but I often find myself either forgetting or just laughing at their stupidity.
The best-worst game ever made.

I really do not like this as much as the first one. First off, they lost the jank. The cutscenes are still pretty amusing, if not as wacky (tbf Sonic meeting the president is fucking hilarious). The story is more serious, which is both an improvement and to its detriment. And that's kind of my criticism of everything in this game: lots of "improvements" have been put in place. Some are great, like the lightspeed dash being instant or the Knuckles/Rouge stages being genuinely great this time. However;
Sonic/Shadow stages are more linear and strait line speed-focused, which may work for some but skipping vast parts of the level was something that made the original incredibly exciting. The Chao garden is far better integrated, but realising the keys and animals are the only worthwhile collectable in stages leads to my rapid decline in any interest of them once I get bored of Chaos.
Worst of all is the character change. I would be completely fine with the way in which you move from character to character per stage, I'd go as far as to say it IS an improvement from the previous games 6 character stories that are all just the same game again but varyingly worse than Sonic's. This is only in theory. In practice, Tails and Eggman exist. The mere presence of their stages in this game, just knowing once I beat a genuinely fun Sonic/Knuckles level, I'll be back to the horrendously slow prison of the mech...
Fuck Tails and Eggman for ruining this otherwise solid sequel.

I haven't played Unleashed though it is absolutely on my wish list. Until that day comes, this is my absolute favourite 3D sonic game for one reason alone that should define every game in this franchise: speed. But above even that, it has everything you could ever want or need, not just from a Sonic game but from a 3D or 2D platformer in general. Methodical 2D precision sections, cool powerups (except the cube ofc, which may as well just be a switch you can press in the level), one of the franchise all time greatest soundtracks which is really saying something, and I even love the hyper speed automated segments. They're like a well-deserved reward. Currently replaying it for 100%, and while some of the red rings are stupidly placed (why on earth would you ever make me use the frenzy wisp for precision platforming), I get that they're totally optional.
Nostalgia is a powerful drug, and I am still very much addicted to this game.