Sonic Mega Collection

Sonic Mega Collection is a compilation of Sonic the Hedgehog games for the Nintendo GameCube with the addition of many extras.

Seven Sonic games: Three lock-on modes from Sonic & Knuckles: Unlockable Sega Genesis games:
 * Sonic the Hedgehog
 * Sonic the Hedgehog 2
 * Sonic the Hedgehog 3
 * Sonic & Knuckles
 * Sonic 3D Blast
 * Sonic the Hedgehog Spinball
 * Dr. Robotnik's Mean Bean Machine
 * Sonic 3 & Knuckles
 * Knuckles the Echidna in Sonic the Hedgehog 2
 * Blue Sphere
 * Flicky
 * Ristar
 * The Ooze - JP only
 * Comix Zone - JP only

Sonic Mega Collection Plus
Sonic Mega Collection Plus is the PlayStation 2, Xbox, and PC version that includes all of the original content plus the Japanese only unlockable games: The Ooze and Comix Zone. The game also has six Sega Game Gear games not found in Sonic Mega Collection. This version also has an in-game saving feature along with new artwork and movies.

Six Sega Game Gear games:
 * Sonic the Hedgehog
 * Sonic Chaos
 * Sonic Drift
 * Sonic Labyrinth
 * Dr. Robotnik's Mean Bean Machine
 * Sonic Blast

Unlockables
Many games have to be played multiple times in order to new games, but they don't necessarily have to be played. Simply enter the game and once it has started, exit out and repeat.