In this post-modernistic masterpiece, we follow the turbulent inner struggle of Sonic T. Hedgehog as he grapples with issues of identity, a fitting follow-up for the first game's exploration of his sexuality and search for belonging in a world he does not feel like he fits into. He is constantly besieged by a mysterious apparition known only as "The Shadow" - which, to educated players, should be immediately apparent as an overt application of Jungian psychology, as The Shadow represents the parts of Sonic that he desperately tries to not aknowledge, as well as manifesting his insecurities: where Sonic attempts to be heroic, noble, and fast, The Shadow is a cruel, villainous sort, heralding Sonic's constant inner battle against his latent nihilism and pro-capitalistic attitude, an aspect of his character that is also explored in his obsession with "Rings", the main currency of Hedgehog Earth. Worth noting is that The Shadow does not have Sonic's speed - instead opting to have his racing prowess augmented by a pair of rocket-enhanced shoes, symbolizing Sonic's constant insecurity and fear - running is all he is good at, what if he one day could not run as quickly without aid? What use would there then be for him? He literally can not see himself as anything else than someone who runs fast, and his self-esteem suffers for it. There are some Kafka-esque overtones to this subplot, punctuated by Lynchian dream sequences in which Sonic takes on the appearance of Doctor Eggman, his therapist, as he rampages through a derelict shipyard in a large robot, freeing animals from the cold clutches of other, slightly smaller robots. These scenes are often contrasted by the non-chronological vignettes wherein we play as Tail The Hedgehog; these ultimately only exist to expand upon the backstory of Sonic's relationship with Jamie Hedgehog, however, while the Doctor Eggman scenes tend to revolve around Sonic's trust issues. There is also a minor subplot concerning Knuckles The Hedgefund, and his supposedly controversial inter-racial relationship with Rogue The Boat, but this is ultimately only inserted to make the game an appropriate length (five and a half hours) and these stages were all removed in the Director's Cut.
All in all, this is a classic that you owe it to yourself to experience. I have faith that if this game had been released before Johnny "Jaws" Ebert died, he would have realized that sometimes, video games CAN be art - SEGA's creative mastermind, director Shigeru Miyamoto, has certainly proved that much with this interesting (though thematically dense) narrative.