It's hard to recommend to Sonic fan or not due to small replay value and a weak soundtrack.
The gameplay is not kart-based or even close. You play as a Sonic character, there are not very many selectable character or tracks, then you choose a track and run through it. The characters run pretty fast, but also that is about all you'll be doing is running. You can jump but there is not all of the items and other cool features Mario Kart has. If this game was trying to be Mario Kart, it's not due to lack of items, characters and courses. With all of the things Sonic R lacks, it's very hard to give it a good score in value. The multiplayer matches can't hardly help it either, due to the fact that you'd probably be playing Mario Kart multiplayer anyway.
The graphics are impressive. They are pretty smooth and look better than a Playstation game. Honestly, Mario Kart is a tad better because of the more detail they cared to put in the levels. Sonic R's level design is all pretty generic. Like ancient Egyption ruins courses, or a factory course, it's all pretty basic and nothing we haven't seen before.
The music is just so annoying that you'll probably find yourself putting your TV on mute because the sound effects don't help either.
Too bad this game lacked in about everything it offers, otherwise it would've been a great game. It's hard to recommend to buy, even for a Sonic fan because it just isn't worth more than a week. Rent instead. Or buy Sonic Gems Collection, which was Sonic R and more games.