To preface: I did not expect to enjoy this movie. I was pleasantly surprised. Contrary to everything I went in expecting, the film is genuinely charming and sufficiently self aware. I also enjoyed that Sonic in this film is not as ~RADICOOL~ as he is portrayed in Sonic Adventure 1, 2, and so on. He's actually kind of a lonesome dork, and that is to the film's credit.
I review this as a children's film, by the way. It's overall enjoyable to watch as an adult, to be sure, but it is clearly meant to be a kid's film. It's inoffensive and doesn't reinvent the wheel, but what it does, it does well.