'Sonic 1 Delta' (2020) by Team Delta (Hack)
Features new sprites, returning beta content, and new special stage functionality. Part of the @SHContest in 2020.
https://archive.org/download/SonicHackingContest2020

'Sonic 2 CD Remix' (2018) by Pacca (Demo Hack)
What if 'Sonic 2' had fully features 'Sonic CD' time jumping? This proves it out with several stages.
https://drive.google.com/drive/folders/1_2L8xe2gcc2ElFn2huhSgudRNOEQL5LF?usp=sharing

'The Emerald's Awakening' (2012) by Bluefox Team (Demo)
A long in development fan game. This is the 2012 SAGE demo (with 2015 widescreen support update)
https://bluefoxteam.wordpress.com/downloads/

'Persian Localization' (2024) by Team Persian (Generations Mod)
aims to fully localize the game into the Persian (aka Farsi) language for the Persian audience.
https://shc.zone/entries/contest2024/1157

'Junio Sonic' (2021) by @motorroach (SRB2 Mod)
Play as a Sonic styled from the 'Sonic CD' opening.
https://mb.srb2.org/addons/junio-sonic.557/

'Silver The Hedgehog' (2020) by @Latapostrophe (SRB2 Mod)
Adds the ability to play as Silver, with his own unique abilities. Footage by ThePinkGalaxy55.
https://mb.srb2.org/threads/silver-the-hedgehog-v2-6.27523/

'Sonic Adventure 3: Full Dark Sonic' (2009) by yvarthecreator
Features 'Sonic Rush' styled gameplay, 30 stages, adventure fields, extra modes and more.
https://archive.org/details/sonic-adventure-3-full-dark-sonic_202105

'Sonic 3D in 2D' (2020) by Sotaknuck
Reimagines Sonic 3D Blast plot and levels with style and structure closer to the games that preceeded it.
https://sotaknuck.itch.io/sonic3d2d

'Sonic GT' (2020) by NotSoGreedy
A massive 3D Sonic fangame all about speed. 4 huge stages and multiple characters to play as.
https://gamejolt.com/games/Sonic-GT/533291

'Sonic Adventure Blast' (2018) by chubbabubba (Demo)
Aims to capture the feeling of movement in SA1 & 2, while making various changes and additions to make it feel new and unique.
https://sonicfangameshq.com/forums/showcase/sonic-adventure-blast.191/