Rubberduckeycooley (what a name) released his (almost) complete Decompilation of Sonic 1 & 2 (2013).
This is based on Christan Whitehead's "Retro Engine"and requires assets from the official releases to run.
Currently supported are:
iOS Sonic 1 & 2 via the App Store
Android Sonic 1 & 2 via Google Play
Android Sonic 1 & 2 via Amazon
Even if your platform isn't supported by the official releases, you can buy it for the assets (you dont need to run the official release, you just need the game assets)
How to get the game to run (windows): take the data.rsdk file from your legally purchased copy of Sonic 1 (2013) OR Sonic 2 (2013) and place it in the same directory as the .exe file.