Sonic the Hedgehog for the Sega Master System isn't a port of the Genesis version. The levels are different, the enemies fewer, but the idea is the same. Technically speaking, it shows again that the Sega Master System could produce some high-quality games. Unfortunately for Sega in the 80s, the few outstanding Master System games couldn't hold back the flood of NES titles.
The Master System was dead in the US by 1991 but still had a substantial following in Europe and Brazil. I suspect Sonic the Hedgehog was largely developed for sale overseas, it was easy enough for them to release a US version too. The combination of the low-cost Sega Master System II and Sonic the Hedgehog likely swayed a few parents who didn't want to drop $200 on the Genesis equivalent for Christmas.
The Sega Master System would enjoy another seven years of new releases in Brazil courtesy of Tec Toy. They continue to sell a licensed variant of Sega Master System with 131 built-in games.
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