Wow....just, wow.
Graphics: 10/10 This game has such detailed graphics, it's quite simply amazing. There is no blurriness, no blocky-ness, nothing bad at all. I'm not sure why people are complaining about the fact that the drivers are animated with sprites. It looks really great. I like it because the drivers are not all blocky and polygony. Yes, I'm aware that polygony is not a word.
Sound: 9.5/10 The sound is really good! There is a different song for almost every track! The sound effects aren't to original or great, but they're still ok. The voices are really good though! Wario's voice was awesome! It fit perfectly! I don't know why they changed it for Mario Party, but now I'm getting off subject.
Gameplay: 10/10 The gameplay is awesome! The first Mario Kart had a strictly split-screen view, but in this, it's a full screen view, which is really good. Put simply, gameplay = awesome.
Multiplayer: 10/10 Wow. This game has one of the best multiplayer modes ever known. Along with the regular "race against a friend!" mode, which is awesome, it also has a "battle" mode where you throw items to pop each-other's balloons. This is really fun! If you have a few friends, definitely play with this mode first!
Overall: 10?10 This game is awesome! I strongly recommend it to anyone who like racing games, Mario, or video games in general.