If you wanted any of those older digital releases of Sonic 1, 2, 3 & Knckles, and CD, you might want to get them soon, because most of them are getting delisted on May 20. This news comes via a press release from SEGA, which confirmed the delisting of these games across all platforms outside of the Nintendo Switch and mobile.
Specifically, every individually released version of Sonic 1, 2, 3, Sonic & Knuckles, and Sonic CD are all getting delisted from Steam, Xbox, Playstation 3 and Playstation Now. The SEGA AGES releases of Sonic 1 and 2 on Switch will remain, as will Sonic 1, 2 and CD on iOS and Android. The 3DS releases have yet to be specified, but with that digital service ending next year they likely aren’t bothering with it.
Sonic Channel released a somewhat more detailed list of what was being delisted, though while they say Sonic CD will be among the games getting delisted, it’s not on the list. This is likely just an oversight. You can find that here.