Absolutely stellar. I came here with a friend to laugh at how bad it was going to be, but ended up laughing out of genuine delight. Actually very loyal to the games. I liked how they handled his backstory, my only complaint being how rushed the beginning was. The pacing was strange to start off but got way better at the end. Sonic wasn't annoying for once! He was adorable and had a lot of emotional beats (they tried to hit really hard with his loneliness, but I didn't mind it too much). The ending scene with Eggman was funny and set up nicely for a sequel!!! (And the after-credits scene? Literally the whole theater screamed in joy. I won't spoil it!)
TL;DR
Amazing. Adorable. Good amount of adult jokes sprinkled in. AMAZING for a fan to watch. Can't wait for the sequel, if they make one!