The Absolute Best Platformer of that Era.
Sonic and Knuckles is a game with ideas. Many other series have never had ideas as game changing as this. Take Mario; Luigi plays exactly the same as Mario. There are no differences other than one being taller and green.
Playing with Knuckles, on the other hand, is much different from Sonic. His glide attack is made to good use here; levels are designed solely for the sake of BOTH characters. Sonic and Knuckles each have their own story mode, which goes through the same levels, but different parts of those levels. Knuckles is an echidna who guards the floating island that contains the Master Emerald. Tricked by Robotnik, he attacks Sonic in the beginning, but slowly realizes he's been had. I have NEVER seen a platformer with a "betrayal" aspect. That alone made the story great for a platformer.
What's even more interesting is Knuckle's ability to climb. Unlike Sonic, Knuckles can't jump as high. But since Sonic can't climb, there are surfaces for which allow Knuckles to go even higher. Sonic and Knuckles is the last 2D sonic game to focus on the jumping, where 2D installments afterwards featured attacks on ground.
That's where the essence of the Sonic series used to lie; the fluidity of attacking enemies. In the old sonic games, you'd bounce, and could control your momentum afterwards. Nowadays, Sonic game's combat feels as stiff and unintuitive as flying an airplane in GTA San Andreas... but that will be for another review. Sonic and Knuckles proudly reinvigorates the former; use of the fluidity of the jumps in order to get through the levels.
Also, you HAD to defeat enemies to get through levels. All the 2D Sonic Games after this were all about the speed; yes, we know Sonic is fast. But to be honest the gameplay suffers when you make it TOO fast. Level memorization is not as fun as exploration. Thankfully, there is much to explore here; both characters can access different areas leading to some "oh wow" moments as to how well the levels are designed. You'll go through forests, deserts, airships, volcanos, and Knuckle's homeland as well. All the vistas are SUPERB and show of the best that the Genesis had to offer.
*There will be spoilers here so skip this paragraph if you want to not be spoiled... even if it's not much of a plot*
A level that struck me as daunting; Lava Reef as Sonic. Firstly, the level is crystalized, and slowly moves into a "this volcano is erupting" scenario. Afterwards, you see the Death Egg (thumbs up for death star reference) in the horizon with thunder clouds booming around it. The level starts to get precision based; literally EVERYTHING hurts you except the last remains of rock. You keep on going until Robotnik appears... then you realize that these rocks are all you have to rely on for safety! It was definitely a heart-pumping experience, and no other Sonic level beats it.
I could go on and on about how great the levels and interaction between Sonic and Knuckles are, but honestly, I can't do it justice. This is a game you need to play through with both characters. This is a game that is perfection on a whole new level. This is a game that understand not to take things away from gameplay; only to add. That is why this is the closest game to perfection I have ever played.
+ Story- in a world of bland platformer stories, betrayal is rather rare. S&K pulls it off. 4.5/5
+ Gameplay- Tight, intuitive, and keeps a steady flow. 5/5
+ Graphics- Well detailed backgrounds. Best 2D Sonic model yet. 5/5
+ Sound Design- "The Doomsday" is a song I play quite often on my iTunes. 5/5
+ Overall- A near perfect Sonic 2D platformer.