S3K is the peak of Sonic as a franchise. It is one of the greatest platformers ever made. A lot of the things Sonic 2 introduced was done better in 3K. Levels were speedy yet complex, getting Super Sonic and making the game much easier for yourself made being brought back down to earth in Mushroom Hill hit that much harder, and made Hyper Sonic that much more satisfying to obtain. Elemental powerups are better than just 'here is a shield', and the invincibility thing Sonic does if you double tap jump means that Sonic has some uniqueness compared to Tails and Knuckles. The final bosses were better than a walking egg robot you need to hit a couple times to beat. Replayable game considering you have two other characters to play again as. Special stages were leagues better than the tails rapes you in the butt stages of Sonic 2.