Edit (26/07/2021): Fixed typos and improved readabilty.
It was a bit hard to know how to start with this one. Sonic 1 is as straightforward as it gets: go from point A to point B, defeat the big bad and you're done. Thinking about it, I decided to approach it as a player unfamiliar with Sonic, and that this game was their first introduction to everything (you'll understand why very soon.) Sonic 1 is simple, but it has some stuff going on nonetheless!
Starting with the first level, a nature vs technology theme is already present. The various robots have greys and more dark colors, making them stand out a bit from the scenery; even if the player can't tell they are bots from the sprites, these guys strike them as unnatural. If they run into one of them, they get hurt, establshing bots as the bad guys. Sonic's abilities are understood by the player simply by playing the game naturally. They notice that the enemies only get hurt when he's curled into a ball, huh, this blue guy attacks by curling into a ball! Oh he can go fast if I build momentum! And so on. The main theme and the main character's abilties are already established, and without saying anything or stopping the player. Neat!
Image source: Sonic Retro
By the third act, they see a funky guy in a big machine. Even if the player can't tell he's a human, they understand he's stronger than the regular enemies because he has more complex attacks and takes more hits, and thus a bigger bad. When they reach the next couple act 3s he comes yet again, then it's cemented that he's the ultimate big bad and probably the one behind all of the other bots. And there, the big villain is established.
A final detail I'd like to touch on from a playthrough perspective is how every zone gets progressively more industrial, going back to the nature vs technology theme. Keep in mind is thet Labyrinth Zone and Spring Yard Zone switched places during developpement due to balancing reasons. (Labyrinth was found harder than Spring Yard.) Green Hill Zone is a lush, green vibrant place with waterfalls and palmtrees at every corner. A few spikes here and there, but no prevalent machinery. Marble Zone and Labyrinth Zone have man-made (or mobian-made) infrastructure, though those didn't overtake nature, and they show some decay with a lot more mechanical traps. By Spring Yard Zone, the scenery completely changed to fully artificial, even if the vibrant colors are still present. Nature is almost completely gone, the player is approaching more and more the lair of the beast. Star Light Zone and Scrap Brain Zone are pretty much the final point with greyer, darker colors; more visible bare machinery, deadly traps and robots everywhere. All of this without telling a thing. You can achieve so much by just, showing stuff instead of telling in your story. Not saying that all stories should not tell you anything or that showing is inherently better than telling, but the simple stories of these Genesis games really benefit from this type of storytelling.
The game manuals add some neat depth and context to all of the player has seen. The Japanese manuals are already superior because they offer color and cute marker/crayon doodles of the characters. Sorry westoids!
Translated by Windii
Dr. Eggman, the evil genius scientist, has begun to embrace his evil ways again. "Sonic... that annoying, cheeky hedgehog. He's the one who's always ruining my great plans. This time, I'm going to crush him with the power of my science! Heheheh..."
South Island is a treasure trove of gems and ruins. It is also said to be the island where the mystical "Chaos Emeralds" lay dormant. The Chaos Emeralds are a super-substance that gives energy to all living things. They can also be used to create nuclear weapons and laser beams through science and technology. However, no one knows how to obtain them. This is because South Island is a moving island, and the Chaos Emeralds exist within the distortions that the island creates.
Then one day, danger came upon the island. Dr. Eggman and his henchmen landed on the island. "Hmph... I'll make sure to get my hands on the Chaos Emeralds, even if I'll have to dig up this entire island." Dr. Eggman built a huge fortress on the corner of the island and began to develop it.
"Eggman! You still won't learn your lesson?!" Sonic rushed over after hearing the rumors. Dr. Eggman's harassment was a regular occurrence. He has always been dealt with so far. Dr. Eggman may think of Sonic as his nemesis, but he's no match for Sonic.
But this time, oh my... Something's not right. "You see, Sonic?! This time it's different. I've turned all the animals on the island into robots." "Y-You guys!" "They'll all do what I tell them to. In other words, the whole island is your enemy. Hahahahaha... cough cough. This time, the whole world will be mine."
This is terrible! Go, Sonic the Hedgehog! Everyone is waiting for your help.
Image and translation source: Sonic Retro
Now what do you learn? The main villain Dr. Eggman/Dr. Robotnik is an evil genius that uses science for his own bad intentions. The nature vs technology parallel comes back with a lot of stuff here. He's a human, and the hero that stops him is an animal; so are the creatures that Eggman enslaved. He abuses natural power sources (Chaos Emeralds, animals) to power his machines. He took over a part of South Island to build his forteress, and weaponized most of the island against him. Not anything groundbreaking, but since it's the main theme I must go over all of this. Interesting stuff is the mention of South Island, people who watched the OVA might recognize the location. Also, Chaos Emeralds have had such different explanations about their properties and powers and all of that biz, and this is by far one of the most interesting ones. "Chaos Emeralds are a super-substance that gives energy to all living things" Huh! The last thing is that Eggman and Sonic has a pre-established rivalry, making it a bit of a personal thing for these two. Eggman was a repeat offender since Sonic 1 and yet Sonic could still garner some trust for this guy in some media. Whatever that says about Sonic's nature can be positive or negative from a subjective point of view, but hey! Interesting!
Crush Dr. Robotnik!
Dr. Ivo Robotnik, the mad scientist, is snatching innocent animals and turning them into evil robots! Only one tough dude can put an end to the demented scientist's fiendish scheme. It's Sonic, the real cool hedgehog with the spiked haircut and power sneakers that give him super speed.
Help Sonic fight hordes of metal maniacs and do the loop with the Super Sonic Spin Attack. Speed down twisting tunnels and swing over dangerous booby traps. Leap across lava pits and dodge burning rocks. Then splash through the chilling waters in an underground cavern. And if you're lucky, you can warp to the secret zone where you spin around in a floating maze! Your greatest challenge lurks in a secret lab where you come face to face with Dr. Robotnik himself!
Spin through space, loop 'til you're dizzy, save the animals and become the super hero. Be Sonic! Be atomic!
Image and transcription source: Sonic Retro
First of all, boo, boring manual. Not the content of the text but just presentation. Second of all, this removes a lot of extra information present in the Japanese manual, though, the essentials are there. I have nothing to add here I didn't talk about in the Japanese section, but you can tell these guys really tried to make Sonic be as cool as possible. I appreciate that they described the speed and danger of this quest, and created the Robotnik name to make the villain seem more threatening. It paints a more thrilling and cinematic adventure than in the Japanese manual. And that's fuckin cool.
Sonic 1 is such a simple game, but it layed the foundation of everything Sonic. The main themes and mechanics of this entire series got established in that cartridge with a few megabytes of storage! (Fun fact, this web page is larger than Sonic 1). The story was simple, and that's okay, you learnt everything you needed to know naturally by playing. Yet, there was still a sense of mystery, mostly only present in the Japanese manual sadly: the power source of the Chaos Emeralds, and Sonic and Eggman's past rivalry raise some questions. If I found interesting things to talk about when your story is almost as simple as beat the big bad and gather the magic stones, ya did good.
- Gap