Sega has done what Nintendo won't, encouraged fans to "keep making great" Sonic fan games. Their encouragement has kept fan-made games alive while Nintendo squashes every game that uses their IP.
Recently, we saw Nintendo take down Pokemon Uranium get taken down, the fan-made Metroid 2 remake, No Mario's Sky get a DMCA notice (but that didn't stop them), and over 500 other fan-made games housed on a gaming site.
Instead of killing things, Sega joked that they would be sending a DMCA notice to the fan-created 3D Sonic the Hedgehog game, 'Green Hill Paradise Act 2,' but instead gave them the thumbs up and thanks to that, we have Sonic Utopia.
The games creator, The Great Lange, detailed the creation (as seen above) as the following:
"Sonic Utopia is an experiment that not only tries to expand on Sonic gameplay in an intuitive way in 3D, but also aims to capture the best of Sonic's style and tie it together in a cohesive experience. Nearly everything in this demo, from art to sound to the gameplay engine, was made from scratch.
I created all of the models, animation, and most of the textures and sound, as well as the music.
The 3D Sonic engine and the gameplay driving this vision was created by my programmer fellow Murasaki."