Best Mario Kart ever.
This isn't an understatement. The DS has been out for about three years now, and several solid games have been released.. but none are as addictive or enjoyable as Mario Kart.
Since it's frustrating to read long paragraphs, I'll make it short.
Gameplay is short and sweet. Most races last three laps and all three laps are challenging as the AI constantly engages the player with item attacks and boost. The vehicles are well balanced, and all karts have a different feel to them. You may need getting used to each one. Gamers should also try the various missions and battles in the game.
The graphics are solid. All karts are rendered in 3D, with only minor details in 2D to allow the DS to run smoothly. The game will nearly always run at 60 fps with hardly any slow down.
Sound is memorable, but I wouldn't say it's a masterpiece. The small sound effects like the "bling" SFX when you get an item is rewarding, but the music for the races isn't especially memorable. The sound is great, but not perfect.
All in all, Mario Kart DS is a must-have if you own a DS, and I don't see kart racing games getting any better than this.