It started it all.... this game was the one.
Pros: Colorful, bright, and great 16-bit graphics, Classical Great Music, Speedy, intense, and spunky, Ring Count makes you feel invincible (If you get rings and lose them, you can get them back. They are no health bars but with the power of rings... you can feel invincible and you don't have to worry about losing health when you can easily get it back though some enimes and obstacles are strong enough to kill you), sound effects are nice and crispy, level designs match speed and is overally superb.
Cons: Can be hard, special stages are hard. But that makes the game a challenge. Graphics: At it's time, the game was praised for being colorful, bright, beautiful and being one of the best looking games on the Genesis. Everybody loved the graphics and along with the speed... the background is too fast to see but you can still see it. The backgrounds are.... pretty detailed.The marble zone has like 10 million bricks. They are a ton of rings, large special stages, and a lot of background. The graphics are still good... yet great after all these years (15 years).
Gameplay- Speedy, Intense, and Spunky. Jumping on enemies is more cool than how Mario does it. The speed is the main part of the game. This game brought speed to platformers. Many people were sick of going slow... so when this game came out they witnessed intense speed. Sonic at full running speed (with no boost pads) may not seem as fast as before but try go inside tunnels at your highest speed. You'll see true speed, alright. You'll see it. No spin dash but that's because Sonic Team never thought of the idea back then. Spin attack is furious. As what you execpt from a hedgehog, they look like balls. Sonic doesn't! Sonic curl up to a ball and doing it on enemies they will explode. In boss battles, it takes more than one spin attack to bust them up... but Duh-Deh-Der! They bosses. The boss fights are fun to complete. Animals saving the world. This game probably started the whole "when animals go on adventure" thing. The bad camera from 3D Sonic games aren't here but this is 2D so what do you execpt (It's great to see no bad camera! Damn the camera in 3D Sonic games!" Remember this: Sonic is one crazey fast lil' dude. The Green Hill Zone is the best level... the first level in the WHOLE Sonic franchise.
Sound: Excellent music of course. It's extremely classical. Green Hill Zone music is very well done. (Do-Do-Do-Do-Do-Do Doooooo- Do- Do... Do-Do. Ehem... sorry I'm humming it.) Sound effects match the game well. And everything in the games' sound is 100% classical. And that is a good thing.
Overall: It started it all. I'll miss Alex Kidd but Sonic is better in my opinion. Some people hate 3D Sonic... but you'll love this. Prepare for a fast, speedy, and intense game! This is why people like Sonic!