Why are we questioning this when his name clearly states he's a hedgehog? Isn't that like asking Chance the Rapper what he does for a living? Well, it turns out the reason the cinematic Sonic looks so off is that he might be an alien. They hint at this in the trailer, when Sonic refers to Earth as "your planet." And in an interview with the film's location manager, he states that the story is like E.T. because it's about a "small town coming together to help the sheriff save our alien from the bad guys." And to be fair, if Twitter had been around in the '80s, people probably would have similarly complained that E.T. is basically a 90-year-old man's genitalia with eyes.
Now, this interpretation contradicts the games' canon. In the official origin story, Sonic was "born on Earth in the early 21st century, in the town of Hardly, Nebraska," and his mother and five sisters lived in a bush next to a fast food restaurant, where they survived on "burger scraps, milkshakes and the occasional slug or bug." So we'll either get Sonic the Alien Who Somewhat Resembles a Blue Hedgehog, or a depressing tale of an impoverished Sonic scrounging for garbage with his single mother.