I played Sonic and All-Stars Racing Transformed back in the day and that was the first kart racer I ever owned or played more than a few sessions of. I feel like the genre kind of peaked with that game, and not just because you could play as Wreck-It Ralph in it. I know you have water skimming and flying in this game too, but it's not the same without the vehicles also changing into boats and planes. It feels more like an afterthought. And there were tracks that actually changed from one lap to the next, like a boardwalk would get smashed so you'd have to go into boat mode for that section. Plus, featuring characters and tracks from across Sega's lineup made the guest characters not stick out like a sore thumb like they do here.
This game does some neat things, though. I like how you can lose rings by smacking into the guardrails, hiding your place when you get close to the finish line is a smart idea, and the hold-the-needle minigame to get a start boost is my favorite approach to that all the ones I've seen. I also like that the lobby is a physical space where your characters hang out in their cars, instead of just existing as a list of names or whatever.
Speaking of Wreck-It Ralph, though, I always found it interesting how the qualifying race depicted in that movie seems to take the racers on a grand tour of the entire Sugar Rush world, as opposed to being confined to single biome like you'd expect a typical kart racer track to. And it made me think about how a real kart racer might make such a thing possible, and I figured either the tracks would all be part of a single overworld and have special detour routes connecting them that only open up for the mega-race, or there would be portals that appear in place of the finish line. So it's especially interesting to me that Nintendo and Sega have, within months of each other, released actual kart racers that take those two respective design routes. Unfortunately in practice they both kind of feel like silly gimmicks.
Also, there's something fundamentally wrong with the world that Mario got a kart racer with rail grinding before Sonic did.