The Sonic fandom is one of the most loyal and hardcore fanbases in all of gaming history, and while Sonic's history is something of a chequered one, the fan loyalty, especially to the original 16-bit era, has never died away.
As a result there's a huge modding and rom-hacking community, one endorsed by Sega (you can submit and play rom hacks to the Steam Workshop, you know), and each year the best of the best creations are showcased at an online event known as the Sonic Hacking Contest.
One of the best ways to experience the entries, in my opinion, is to check out SomecallmeJohnny on YouTube, he always does a very entertaining daily stream of the whole event, playing through all the contest entries, and giving his thoughts and opinions along the way, along with special guests.
But you can check out all the entries, and vote for your best, on the official Sonic Hacking Contest website. Here you can check out the various entries and teams, and even download them and try them for yourself.
Some of the more interesting entries that have caught my eye this year include a port of Emerald Coast to the much maligned Sonic Forces, Sonic 1 Remade, which is a total overhaul of the original Mega Drive game, and Amy Adventure 2, because, you can't have too much Amy Rose, right?
So if you haven't already, check out the Sonic Hacking Contest and vote for your favorites, the event is on now and voting is open.