The stories are divided into three gameplay styles: fast-paced platforming for Sonic and Shadow, third-person shooting for Tails and Eggman, and action-adventure exploration for Knuckles and Rouge.

Adventure 2 received positive reviews, with praise for its gameplay variety, visuals, and music but criticism for its camera, voice acting, and plot.

[5] The characters can obtain permanent upgrades that grant them new abilities; for example, one upgrade allows Sonic and Shadow to dash along a sequential trail of rings to reach distant platforms, one gives Tails and Eggman hover jets that slows their descent to cross large gaps, while another lets Knuckles and Rouge dig into the ground to uncover treasure and Master Emerald pieces.

From the moment they hatch, their stats can be increased with Chaos Drives or small animals, found in the main stages, which empower them to compete in karate[7] and racing minigames.

[15] Doctor Eggman learns of a secret weapon from the diary of his deceased grandfather, Professor Gerald Robotnik, and infiltrates a high-security Guardian Units of Nations (GUN) facility to revive it with a Chaos Emerald.

The weapon—Shadow, a black hedgehog who proclaims himself the "Ultimate Lifeform"—offers to help Eggman conquer the world, telling him to rendezvous at an abandoned space colony, the ARK, with more Chaos Emeralds.

[30] They removed the hub worlds in favor of linear level progression more in line with the older Sonic games,[31] and divided action and exploration sequences among the characters rather than mixing them.

[30] The levels, drawn from Maekawa's story and setting,[20] were inspired by American locations such as Yosemite National Park (where the team vacationed) and the San Francisco Bay Area.

[30] The month Adventure 2 was to be released to manufacturing, one artist suggested adding Green Hill Zone, the original Sonic the Hedgehog's first stage.

Sonic Team USA gave Chao the ability to socialize and interact,[18] which Naka felt "took [them] a step closer to a real artificial life form".

[42] Senoue began writing in April 2000;[41] he worked closely with Sonic Team USA regarding Adventure 2's structure, design, and characters.

While he enjoyed studio work, Senoue described the last three months as chaotic, as he had to travel between Tokyo, San Francisco and Los Angeles within weeks to write and record music.

[28] Sega released the trailer online when it launched Sonic Team's website on June 30,[51] and allowed journalists to play a demo version in December.

[31][52] Early copies of Sonic Team's Phantasy Star Online, released in Japan in December and worldwide in January 2001,[53][54] were bundled with the demo.

[90] Four-Eyed Dragon wrote that the game "is simply jaw-dropping beautiful," citing its detailed backgrounds and scenery and the characters' extensive color palettes.

According to Ahmed, the music was an improvement over Adventure's "campy glam-rock and J-pop soundtrack", with less emphasis on lyrics,[3] while Liu appreciated its more "understated" approach.

[90] Four-Eyed Dragon called the music "an eclectic mix of orchestrated masterpieces, guitar tunes, and melodic hip-hop voices" that "gracefully fill the game's ambiance to a perfect pitch.

[94][95] However, Shane Bettenhausen of GameSpy saw Adventure 2 Battle as noticeably superior; in addition to its upgrades, its action was better suited to the GameCube's controller than the Dreamcast's.

[106] Iizuka described the loss of first-party development benefits as the greatest challenge of the third-party transition, as his team "no longer [had] the ability to control what we need[ed] to make our games".

[b] GameSpot and Kotaku deemed it a satisfying conclusion to Sonic's run on Sega hardware,[127][131] and Game Informer considered it a worthy sequel to Adventure.

[135][136] While IGN praised the gameplay variety,[129] Kotaku noted that many only like the Sonic and Shadow levels;[131] retrospective reviewers have criticized the other characters as frustrating and cumbersome.

[80][141] The Escapist and VentureBeat called the story nonsensical,[67][80] Destructoid said it "almost feels like work to get through",[122] and Vice jokingly compared it to a Bob Books take on Armageddon.

[140] However, VentureBeat praised the good-vs.-evil presentation as clever and adding unexpected nuance to the villains' motivations,[67] and Rock Paper Shotgun said the story was one of Sonic's best despite some melodramatic moments.

[62] VentureBeat wrote that Adventure 2 did not hold up to modern standards, finding its camera and reliance on trial-and-error design outdated,[67] and Destructoid said it was only redeemed by how engaging the Chao Garden was.

[i] Nintendo Life said Adventure 2's many "bizarre design choices" made it endearing,[139] and Kotaku said it "felt equal parts triumphant and bittersweet...

"[131] Following Adventure 2, Sonic's critical standing began to decline,[142] which VentureBeat attributed to Sega "depending on stupid gimmicks to sell their most iconic property" following the third-party transition.

[36] Senoue and the band Hyper Potions produced an Irish-themed remix for a collaboration between Jacksepticeye and the Sonic social media team on St. Patrick's Day 2020.

[147] The original is a selectable song in Sega's Samba de Amigo: Party Central (2023), a rhythm game which includes a City Escape-based stage.

[149][150] Kotaku regarded Generations's City Escape as one of the most impactful moments of 2011,[151] and PCMag considered it a highlight, a "prime example" of Sonic Team drawing inspiration from the franchise's history.

[178] Although it mostly follows Adventure 2's story, it features some differences, such as the absence of City Escape and Gerald Robotnik appearing alive in the present rather than being limited to flashbacks.