Super Mario Kart started the franchise from humble beginnings. It was kind of a sleeper hit, and the reason I say that is that while it wasn't very polished compared to games like Super Mario World, it still spawned multiple sequels.
I am pretty much unchallenged by anyone I know although I'm the only person I know personally who likes it nearly as much as I do. I'd say my favorite entries would be Mario Kart: Super Circuit and second on the list would be Mario Kart 64. I think the GBA one was just glorious with extremely polished gameplay and presentation, and
tons of replay value. But that's just a nice overhaul of an already good franchise. This new GCN sequel, however, is by far the most disappointing entry I've seen. It should be called Nintendo Wacky Racers. I don't know about any of you, but I fell in love with the franchise because of the gameplay, but this two-seater crap is going to really hamper the gameplay no matter how you look at it. It will be frustrating to drive while having another character throwing around items, maybe even obstructing the view. And likewise, throwing around items with aim will be difficult when your driver is swinging around sharp turns, jumping ramps or road-bumps, and avoiding other "karts" (if you can call them that now) and swirving everywhere, but that's only if the driver's any good.
I would have liked it if the characters were riding their own separate karts and if they did some major lightening up on the frilly vehicle designs. They called the first games "Mario Kart" because of the fact that they're driving go-carts. In the words of whoever invented this phrase: "If it ain't broke, don't fix it".
Oh, and where did all this talk about cel-shading come from? This game isn't cel-shaded anywhere... The only reference I can think of is that Nintendo took a simularly HUGE risk with cel-shading Zelda like they are doing with changing the trademark gameplay of the MK game dynasty. But the GCN-MK-change is different, as it's stupid no matter how you look at it. The only real redeeming quality about this game is the 8 player LAN and even
that ain't all it's cracked up to be as earlier posts point out. I wouldn't mind the change in gameplay or even if they decided to change the go-carts into filing cabinets as long as Nintendo passed it on as a different game altogether insteading of tarnishing the name of Mario Kart *holds head up proudly like the noble and loyal Mario Kart fan that he is*
(Oh, and Yoshi needs to have his own kart. Yoshi rocks the track's friggin ass off, man. He's WAY too cool to have the pink what's-her-garden-hose-face's name riding on his back. That's for another type of kart (with a backseat and shock absorbers) and for later on, hehehe...

Hey, Yoshi's got a girl too people! Don't believe me? Why do you think they made a tennis court in Mario Tennis 64 featuring them two? I choose Yoshi for every Nintendo-character-franchised games, including Super Smash Bros., Mario Golf, Mario Tennis, Mario Kart (obviously), Mario Party, etc.)