A fun family film which doesn't take itself too seriously. There is something in this movie for everyone, as it does an excellent job of balancing accessibility to those new to the Sonic franchise, with fanservice to nostalgic veteran fans.
As a family film, some of the gags are a bit juvenile (fart jokes in particular) to keep the kids interested, but this happens infrequently enough to avoid alienating more mature viewers, and is overshadowed by the simple yet compelling plot, as well as the touching overtones of loneliness, friendship, and purpose that play out between Sonic and his human companion.
Jim Carrey - Doctor Robotnik/Eggman - is particular in his element in this movie, as he is able to really chew the scenery and take full liberty with his famous physical comedy. His character is that of a complete fruitcake with a narcissistic streak, that manages to be both menacing when appropriate and enjoyable in other moments.
In summary: it is a wholesome, light-hearted movie with broad appeal. It is strongly recommended to watch the film, even if you are not a Sonic fan. Jim Carrey is a fantastic pick for the villain, the story is simple but effective, and in some cases quite touching. An excellent case study in how a video game movie should be made. Could the video game movie curse finally be broken?