Sega bundled Sonic the Hedgehog with the Mega Drive starting in mid-1991, kicking out the previous pack-in (Altered Beast) in the process. The Genesis sold five times faster after the swap. Within eighteen months Sega held a 55% share of the North American 16-bit market. Nintendo had not been here before, and they were not happy about it.
What it is
A six-zone, 18-act 2D platformer where Sonic, a teenage blue hedgehog with attitude, runs and jumps through loops, ramps, and corkscrews to stop Doctor Robotnik from converting woodland animals into robots. Each zone is themed (Green Hill, Marble, Spring Yard, Labyrinth, Star Light, Scrap Brain) and ends with a Robotnik boss fight in a single-screen arena. Special stages bring chaos emerald collection. Six emeralds, the good ending; fewer, you get yelled at.
Why it matters
Sonic the Hedgehog is the answer to the question "what does platforming look like at speed". Mario stops to think; Sonic doesn't. The level design is built around momentum: roll into a loop, hit a ramp, fall through a sequence of hidden platforms, end up two screens to the right with no idea how. Sega Technical Institute's Yuji Naka built the engine around a single-pixel collision system that let Sonic interact with curves, which is what enables the loops everyone remembers and almost no contemporary platformer attempted.
It also sounds great. Masato Nakamura (of the band Dreams Come True) wrote the soundtrack, Green Hill, Star Light, the Marble Zone tunes, that has aged into the Mega Drive's sonic identity. The Mega Drive's Yamaha YM2612 FM synth gives those tracks a brassy, slightly aggressive timbre nobody else's hardware could produce.
The catalogue position
The first Sonic sold about 15 million copies on the Mega Drive, which made it the best-selling game on the platform. Sonic the Hedgehog 2 (1992), Sonic 3 (1994) and Sonic & Knuckles (1994) iterated on the formula and arguably surpassed it. The original is the best entry point: shorter, simpler, less frantic than Sonic 2, more focused than the Sonic 3 / Knuckles lock-on combo.
Worth playing in 2026?
Yes. The Mega Drive original is the canonical experience. Sonic Origins Plus (2023) bundles the first four games with QoL improvements like the missing Drop Dash and modern save states. Original Mega Drive carts of the first Sonic are extremely cheap (under AU$15) because Sega printed millions.