Today, SEGA released the anticipated Sonic 1 mobile port by Taxman (Christian Whitehead) to iOS and Android. This re-release of Sonic 1 is built from the ground up, with remastered graphics, playable Knuckles and Tails, and all the good stuff Taxman usually puts into his ports. If you already owned the old port, you can download this new version as a free update. Also, the Sonic 2 port is due to be released in the coming weeks.
I am playing the port right now, and I can tell you, this is a real nice job. The game has colorful menus, and everything feels silky smooth in controls.