Sonic the Hedgehog 2 is a revolutionary video game, in that it has Tails in it. Other than that, it's pretty normal, I think.

The game also happened to introduce the concept of a set release date to the gaming industry - a Tuesday, at that. Just imagine the world we'd live in if games were put on shelves whenever they showed up. We'd live in shambles, right?
...What do you mean mom and pop stores in Europe still do that? That explains the constant early dumps of Switch games.

Sonic 2 is an excellent follow-up to the first game, in that it took everything the first game did and made it better. Sonic 1 was a great starting point, with iconic characters and a really fun physics engine that felt exciting to play. Sonic 2 basically took that and made a good game out of it, crazy right?

The Zones are prettier and more interesting here- Emerald Hill is a solid successor to Green Hill that feels inspired but stands out on its own, Chemical Plant and Casino Night are some of the most memorable zones in the series, and the Death Egg is iconic, even if it's kind of a barebones level here.
Unlike Sonic 1, the Special Stages are actually kind of fun to play. They actually utilize the character's 'gimmick' of speed in a way, and can be somewhat tricky in a way that doesn't feel too dumb. Just a little bit dumb.
Tails is an excellent addition as a character to the series, though functionally, he's pretty damn barebones in this one. But he's Tails so it gets a pass.
Adding a reward for collecting all the Emeralds, beyond a good ending, is an excellent move that encourages players to push through a tough game for a reason other than seeing a different screen at the end.
The Zone count shifting from 3 to 2 made the game a lot less monotonous and gave room for more new environments, which was a much-needed change.

So if you don't get the gist, the game's really darn good. And you know what's better? Sonic did a good successor to their first game, but Mario couldn't get it together until the third game! Truly mind-blowing. Genesis truly does what Nintendon't.

Oh, you know what else is cool about Sonic 2? The prototypes. Man I love seeing Sonic prototypes, it's insane how much we know in-depth about the game's development. It's so darn cool to learn about that stuff.
Even cooler is that the mobile remake, which is a drastic improvement, took a removed level from an early prototype, and remade it as a new level. The mobile version is fucking awesome. All hail Taxman and Stealth, saviors of the hedgehog.