Anticlimax Boss: The final boss is just Eggman in his normal vehicle with four panels that flip around and whatnot. It's a case of dodging predictable attacks and waiting for a chance to hit him, or just taking the hit and then damaging him using invincibility frames (especially on his first hit, where it's legitimately difficult to find an opening). It's not overly hard or very exciting, especially compared to the final bosses of Sonic 2 or Sonic 3 & Knuckles. On top of that, in the American version, the boss music is barely different to the normal one; at least the Japanese/European versions had a proper final boss theme.
In fact, most of the bosses can be seen as this. All of them die in 3-4 hits and can be beaten by strategies that become very straightforward when you see what the game wants you to do against them.
Awesome Music: Depending on the region, gamers were treated to one of two different soundtracks, each kick-ass in its own way (as expected from this series). The Japanese soundtrack,note also used in the original European release composed by Naofumi Hataya and Masafumi Ogata, has that familiar Sonic sound with a dash of J-pop complete with bits and pieces of sampling (notably, Xavier's "Work That Sucker to Death" is used for the boss music); while the American soundtrack, composed by Spencer Nilsen and David J. Young, is more atmospheric and rock-oriented. The past tracks in the U.S. release were unchanged due to technical reasons, which can be slightly jarring.
Also, for whatever reason, the U.S. release lacks a proper final boss theme. It does differ slightly from the standard boss tune, with a few additional instruments and a couple of the sounds, like the sped-up Eggman laugh, at different points in the track, but you have to really listen out for them.
The soundtrack varies per version and region. North America never got the Hataya soundtrack prior to the 2011 re-release; Japan, of course, always had only their own soundtrack (Japanese fans probably aren't even aware there is a different soundtrack, at least until one song from the U.S. soundtrack was remixed for Sonic Generations); Europe got the Hataya soundtrack on the Mega CD version, but the Nilsen soundtrack on the Gems Collection version. The PC version has Nilsen's soundtrack in all regions. The 2011 re-release ultimately fix these woes by having both soundtracks selectable in all regions. However, the intro music for the Japanese soundtrack had the lyrics cut, presumably due to contract issues with the people who sang it. Fortunately, "Sonic Boom" is 100% unchanged.
Best Level Ever: Stardust Speedway, which allows for speedy movement in contrast to the other stages, which are, for the most part, mazelike and slow-paced. It also contains the race against Metal Sonic.
Blessed with Suck: Sonic CD is considered by many to be the best game on the Sega/Mega CD console, and regularly appears on lists of the greatest video games of all time. Many think it would've been even more popular or resonant if not for the failure of the Sega CD itself.
The American soundtrack vs. the Japanese soundtrack, in terms of "superiority". Flame Wars are not uncommon.
This is a particular Berserk Button for Europeans, especially the Brits, who just tend to get whichever region is convenient. They originally got the Japanese soundtrack, yet when both the PC version and Gems Collection came out, that soundtrack was replaced with the American one. Many a European gamer were not happy about the sudden change.
The level design is a big point of contention. Some like the increased focus on platforming and exploration, while others dislike the decreased speed and labyrinthine level layouts.
Ear Worm: The boss music from the Japanese and European versions of the original as well as the Japanese soundtrack option in the 2011 version, which is available in the 2011 version in all regions. "Come on, now! Work that sucker to death!" This is especially in contrast to the nightmarish boss music from the American version.
The JP version of the Stardust Speedway Bad Future theme and its HURHUEHUEHUEing. Even more so in the funkier Generations remix.
Franchise Original Sin: Sonic's first encounter with time travel, the slower paced gameplay, and overly large levels are problems that would be exaggerated in some of the later installments.
Funny Moments: The end to the Stardust Speedway race between Sonic and Metal Sonic. The former just barely makes it under a wall as it closes, leaving the doppelganger to run headfirst into it and mimic Sonic's death animation.
Goddamned Boss: Collision Chaos' boss. All you have to do to beat it is to reach the top of the pinball table, but you might take a lot of time trying to do that, as the flipper's controls are very strange (there is a minuscule delay and the physics are off). Robotnik/Eggman will also throw a lot of bombs that act like bumpers, to keep Sonic from reaching him.
Good Bad Bugs: Debug doesn't work in Time Attack mode. Though it seems to prevent the player from cheating, there is a different bug that will give the player a "00:00:00" time record after the level is completed. This way, the player can easily unlock the game's extra content.
As shown in this video, it's possible to warp from the beginning of Collision Chaos Zone 1 to the end if Sonic has the power sneakers.
In the 2011 version, at least in the Windows Steam version, sometimes Sonic will go through the ceiling. Unlike the Genesis games, though, a restart is not necessary; jumping enough times will get you on top of the level, where running right a certain amount will trigger the goal even though it can't be seen from there.
Another line from the same song is "Doom room, cosmic zoom, heads up Jake it's Sonic Boom!". "Doom room" becomes only more hilarious when you consider the Barrel of Doom from Carnival Night in Sonic 3 (though this game was released earlier, it might have predicted the future... or it was simply a coincidence.
It's Easy, so It Sucks: Aside from the music, the biggest complaint leveled at this game is that the Eggman boss fights are too easy. None of his machines take more than four hits to destroy; most take three, Tidal Tempest technically only takes one, once you get past his defenses, and the Quartz Quadrant & Stardust Speedway battles don't have you attack Robotnik/Eggman directly at all. Bosses in other classic Sonic games almost always required eight hits to beat (mini-bosses took fewer hits to kill and final bosses usually took more).
Just Here for Godzilla: When the game was re-released on Sonic Gems Collection, many fans bought the collection just for that game alone (and given the rest of the games were spinoffs, this makes sense—it also makes sense given the games acclaim as one of the best in the series, yet it never saw a re-release till then, aside from a PC port).
Memetic Mutation: The JP/EU version of the Stardust Speedway Bad Future theme will often elicit a "HURHUEHUEHUE" or variations thereof when it shows up on YouTube.
The JP/EU's stage clear/ending theme also gives us the rather odd shout of "TELEPORTATION YEAH!"
Moment of Awesome: How Sonic tries to stop Dr. Eggman from escaping in the Bad Ending.
Some of the JP music, like the Stardust Speedway and boss themes, can be kind of silly, but no less catchy.
The robotic voice in the Japanese bad future music for Metallic Madness sounds like Microsoft Sam and is basically saying the opposite of the lyrics of that version's theme song, but the song in general (especially the instrumentation) doesn't refrain from reminding you that you screwed up.
The bad futures in both versions, particularly the abrasive industrial remixes in the Japanese version. Sure many American tracks are given creepier reworkings, but most of them still carry a haunting ambiance. The Japanese tracks make it worse by twisting the melodies of its own cute, upbeat themes making the mechanical tone all the more jarring.
Nightmare Retardant: The Bad Futures may look quite bleak, but at least you have the comically ineffectual Badniks. A Kumo-Kumo, for example, will jump into the air and shoot spider webbing at Sonic to restrict his movements, but the broken-down Kumo-Kumos in Quartz Quadrant's Bad Future will just jump up and down pointlessly. Taking the cake, however, is the Taga-Taga. A normal-functioning one will come over to Sonic and launch its spikes. The ones in Tidal Tempest's Bad Future, on the other hand, will retreat upon catching sight of Sonic.
Polished Port: The XBLA/PSN/iOS/Windows Phone 7 ports, as they were built from the ground up from a fan-made engine, it's closely based on the original Mega/Sega CD version, rather than being based on the PC port, has HD support, true widescreen support,note As in, it's not lazily stretched or cropped, but truly extended picture for Widescreen TV screens. Tails is an unlockable playable character, and it even has the option to use the traditional spin dash from Sonic 2 onwards instead of the standard one. There's also an option to switch between the Japanese and American soundtracks. The only gripe is that (due to licensing issues) the JP/EU opening and ending themesnote "Sonic - You Can Do Anything" and "Cosmic Eternity - Believe in Yourself" were replaced with instrumental covers.
A month later, the Steam version was released. However, it wasn't quite as polished as it could've been (graphical problems, no control customization, external video settings), as it's a port of the XBLA version.
Porting Disaster: While not horrendous, the Gems Collection port suffers slightly due to being ported from the early PC version. It is lacking a few graphical effects such as fade out (which were excusable in the PC port as it was meant to help it run on lower end P Cs too but had no place still occurring on much more powerful hardware), the debug mode doesn't work properly due to the controls not being remapped and the music transitions are edited only according to the US release (meaning Metal Sonic will play the "G" future remix if you achieve it). The port was not edited for the PAL version either, meaning they got the US soundtrack rather than the Japanese one they had for the original release.
Scrappy Mechanic: Time travel posts can be used up without activating them if you build up speed for long enough to generate sparks and then lose your speed, or if you cross another time travel post. Since you're running at full speed in an attempt to activate the time travel, you'll need to memorize or stake out the path you're going to take, or put up with the risk of walls, enemies, and other posts getting in the way and ruining the attempt. Very frustrating if you're trying to find Past posts so you can get Good Futures.
Signature Scene: It's very hard to talk about the game without mentioning the Metal Sonic race.
Suspiciously Similar Song: The American boss theme sounds a lot like "Pressure Road" from Ys II. The resemblance is one thing, but they both have the distinction of being nightmarish, cacophonous, and incredibly out of place in series that usually have upbeat music.
Much of the American soundtrack, despite its reputation. Having a playlist of the soundtrack, or better yet the officially extended CD. Nearly the whole soundtrack is ambient folk crossed with alternative rock and extensive vocal harmonies, making it very soothing to listen to as a stand-alone product.
Good Futures. No enemies, a bright and colorful soundtrack, animals living peacefully, and technology being used to benefit nature instead of harming it.
That One Achievement: Savior of the Planet. Getting the Time Stones makes getting the achievement/trophy impossible unless you get the last Time Stone in Metallic Madness Zone 2. Also qualifies as a Guide Dang It for most people.
Luckily, your progress is saved upon entering a Special Stage, so if you exit the game before failing to get the Time Stone and boot up your save file, you can restart at the beginning of the Special Stage and attempt to nab the Time Stone once more.
That One Level: Wacky Workbench, thanks to the bouncy bottom floor. When it comes to getting a good future in Zone 1, it's even harder because of how complicated the path to it is, though at least it's easier to do in Zone 2.
For players trying to finish Time Attack mode in under 25 minutes, Metallic Madness Zones 2 and 3 are easily more irritating than the other levels. Zone 2 takes much practice to complete in under three minutes, as opposed to the previous non-boss levels, which can be beaten in under one minute (and in exceptional cases, 30-45 seconds). Zone 3 has a Platform Hell section at the start, and three extremely tricky enemies to defeat before reaching the boss. You'll be lucky to finish it within two minutes, like the other boss levels.
They Changed It, Now It Sucks: The American soundtrack got a lot of unnecessary flak just for replacing the Japanese one. This mentality even extended to game critics [such as GameFan Magazine, which rated the American version 30 points less than the Japanese version (which got 100%) just for this].
Sega themselves tried to avert this, in the game media. Review copies were beta 920, which is identical to the U.S. release save for having the original music in an attempt to hide the change. It didn't work. Upon hearing that the music was changed behind their backs, a good number of magazines retracted their perfect scores. Whatever your view on the music, most would agree that lying to the press to get a better score isn't exactly excusable.
The common accepted theory as to why Sega changed the music is because they had just built a new music studio for their American branch to use, and the flagship game was used to justify its existence. They probably also didn't want to pay the singers of the Japanese version's vocal tracks, nor for the many, many samples used, most memorably in the boss track. Since the beta had the Japanese soundtrack, it's a possibility that Sega's main American division wanted to show off an American studio's compositions. However, as pointed out on this game's trivia page, when the 2011 remake was being developed, it turned out that the soundtrack with rights issues was the American one. Fortunately, those were worked out. Had they not been, all regions would have had the Japanese soundtrack, which is the default option in the final version).
Ironically, the Japanese soundtrack had the most rights issues, with the opener and closer ("Sonic ~ You Can Do Anything" and "Cosmic Eternity", respectively) outright being replaced with instrumentals, whereas the American soundtrack was completely intact. These issues tend to crop up with Japanese music, due to the strange way rights and permissions work in that country.note For example, Sega doesn't actually own any of the music in Sonic 1 or 2; Masato Nakamura does, and accordingly must be licensed any time they want to use the music, or remixes of it, in other games.