I'm glad GG2SMS exists since the screen crunch makes some harder to enjoy. I need to redo Ristar with that SMS port.
Most of the time the 8-bits version of a 16-bits game was made for owners of the previous system that weren't rich enough to be able to purchase the next gen hardware. It's why Brazil got a ton of 8-bits version of games that never saw any other releases (such as Street Fighter II' on the SMS).
Sonic 1 8-bits is more or less following the same path as Sonic 16-bits (albeit with some changes and added levels like Bridge Zone) whereas Sonic 2 is its own thing. Sonic 3 (and & Knuckles) never got its own 8-bits adaption, probably because by 1994 the 8-bits were too old to warrant making a port.
I can understand why Sonic Chaos and Triple Troubles (Sonic & Tails 1&2 in Japan) are cult favourite because it has introduced Fang the Sniper among other elements.
Here's the full list of GG and SMS Sonic games:
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