Sonic 1 Steam ROM + Sonic 2 Steam ROM + Sonic CD 2011 + Sonic 3

Since Sega decided to delist all versions of Sonic 1, 2, CD, 3 and Sonic & Knuckles from every digital store because of the upcoming release of Sonic

Sonic Origins (for PC) Review

The 10 Best Sonic Games - IGN

Sonic Mania - The Cutting Room Floor

Sonic CD (PC) : SEGA : Free Download, Borrow, and Streaming : Internet Archive

The Android versions of Sonic 1 & 2 have been decompiled and can be played on PC, Page 3

Sonic The Hedgehog's Humble Birthday Blowout Bundle

Review: Sonic CD – Destructoid

What's your favorite versions of Sonic 1, 2, 3, K, and CD? And yes, ROM hacks can count as your favorite versions. - Games - Sonic Stadium

Ports of Sonic CD and Marathon 2 Make Their Way to iOS - MacRumors