Having been disappointed with Sega’s Sonic Origins, I ended up just getting the Android versions of the remakes by Christian Whitehead and settled with that.

Sonic 1 - Remake
Sonic 2 - Remake
Sonic 3 - Emulated (the A.I.R. version is in Beta and looks very buggy, so your best bet is using the emulator included and try out the filters to improve the picture quality)
Sonic CD - Remake

If you want to play the awesome Sonic SMS Remakes, get them here.

Note 1: Sonic CD “Ouya Edition” apk is a “demo” (can be unlocked via a Ouya as a full game) meaning you only get to play the first stage, and I included that as it doesn’t show the directional pad on the screen, but if you use a keyboard (physical/digital), and press the button “Esc” it will be hidden (tested on the “Original” version), anyway.

Note 2: If you need help to get Sonic 3 A.I.R. to work, read the instructions here.

Note 3: “Mod” just means no ads.