Saw it yesterday and it was good. In a lot of ways it was like Detective Pikachu. They're both video game movies. They both had a plot that you could basically see exactly what was going to happen from the trailers. They both hit notes of nostalgia through out the movie without it taking you out of the movie. I enjoyed Detective Pikachu as well, but I'd have to give Sonic the edge as it entertained me more. I had finished the mystery in Detective Pikachu as soon as I saw Bill Nighy and was just waiting for the rest of the cast to catch up (insert idle animation of Sonic tapping his foot) while I was just along for the ride in Sonic.
It wasn't anything revolutionary, you could easily piece together the whole movie from the trailers and I still don't like the "bring the fantastical hero to our non-fantastical world to help curb production costs" trope/template, but it was entertaining despite all that. For having redone the whole character in a few months, Sonic looked really good. I was expecting to see some effects that were some combination of wonky, unfinished, or looking 10 years out of date. I'd love it if there's a feature on the disc about the new and old effects (like did they have to fix the echidnas in the intro? Were there any scenes that would have been in the movie if it wasn't fixed?) but I wouldn't be surprised if they want to let everyone forget that happened. I'm no lore master when it comes to Sonic, but I feel that they adapted and updated him and Dr Robotnik well, never feeling like they skewed out of character or like shined up relic from a bygone era.
I really do hope this gets a sequel so that they can expand on the mid-credit tease. The main problem with the whole "bring the fantastical hero to our non-fantastical world to help curb production costs" thing is, even if they expand the cast with more Sonic characters now they're stuck with some fairly bland human character(s). They could pull a "If I stay here you'll always be in danger/If I stay others will suffer without my help" and toss Sonic back into the world from the intro. I'd be down with that. If they go that route, I still want live action Jim Carrey to show up. The majority of MCU movies end up being CGI with the occasional live action face/head, so I don't think it's too much of a stretch to have Jim Carrey's torso coming out of a CGI Robotnik robot suit/ship (which he basically was in act 3 of Sonic)in a fully CGI world.