MarioKart has been on my must-play list since I first had a Nintendo system, way back in my university days. I've played it on the N64, GameCube, DS, and, now, the Wii. And it rocks so hard.
I've been playing somewhat obsessively for the past couple of days (I've had some time off of work) and have been enjoying myself immensely. I've managed to rack up gold cup trophies in 7 of the 8 cups so far, although only at the 50cc level and have to remind myself to shut the machine down after an hour or so and go do something else, less I play all day.
The best part, for me, is that I finally have a game that my wife will sit down and play with me. She finds the wheel easier to use than the crosspad other versions have required, both for steering and for drifting.
I'm rambling. The point is, go get the game. It is awesomeness squared multiplied by awesomeness cubed.