Download the PC version of Sonic 3D in 2D , install Winlator, and use it to run the Sonic3D2d.exe file. This is generally the most stable method, providing accurate controls and audio.
Also delisted. Currently, your best bet is emulation. sonic 3d in 2d android
While not strictly isometric, Sonic Time Twisted uses pre-rendered 3D sprites on a 2D plane. It feels like what Sonic CD would look like if it were made in 1998. There is an unofficial Android APK floating around fan forums. Download the PC version of Sonic 3D in
The 8-direction isometric movement maps surprisingly well to a touchscreen. The official port included a "Save State" feature and leaderboards, but suffered from input lag. Currently, your best bet is emulation
This is the holy grail. is a fan game running on the Doom Legacy engine. It is a true 3D Sonic game, but it includes a "2D mode" that plays exactly like an isometric platformer.