Just came across this game and it's great! It has a good feel to it, only a few minor annoyances with regards to some added mechanics, but they can be disabled. Regardless, I finished the game as-is.
It's a great mix between the original 8bit levels revisited and demakes of 16bit levels. It always felt right. I grew up with the 16bit Sonic and the 8bit Game Gear version.
My only big grievance is that the second jungle level uses the SMS version of not being able to scroll back down. It would not be an issue if the game didn't keep prematurely scrolling upwards when you jump. It leaves you nowhere to land, and touching the bottom edge kills you. I lost the most lives on this level. The GG version didn't have this, you could fall back down to a lower part of the level.
Lots of playable characters, like Tails, Knuckles and Fang. They can have their own paths in the levels that Sonic can't reach. You can become Super Sonic. Great experience all around.
Besides having replayability (time attack, encore, playing with other characters, ...) there is also a Sonic SMS Remake 2 and 3, will be playing these next.
Played on my Odroid GO Ultra running Rocknix and portmaster.
I rate this 9/10.
https://sonic-sms-remake.blogspot.com/
I believe most of the SMS and GG Sonic games have remakes like this now. I know there's Triple Trouble 16-bit at least,which another good one to check out.
I finished that one first on my PC and was putting it on my Odroid via portmaster when I came across these remakes in portmaster. The SMS remakes website has other demakes and remixes listed!