Often imitated but never ever duplicated is Nintendo's Mario Kart series. Sonic, Crash Bandicoot, and even Bomberman have tried to compete and they never could beat the creators of the entire "kart racing" genre. And this new portable version still seems to stay a step ahead of those cheap copycats.
The first thing that stands out to you are the game's graphics, which can best be described as being in between N64 and Super NES in quality. The nice animated menu backgrounds and sometimes distracting track backgrounds prove that GBA packs more power than a Super NES. If you look really hard you may see a pixelated turtle shell (typical of a 32-bit system *cough* PSone) that reminds you that it's not quite N64 hardware. But the strictly 2-D graphics eliminate any noticeable contrast between the racers and the tracks themselves (the hybrid of 2-D racers and 3-D backgrounds made the N64 version look really weird). The animation's really nice too.
And don't think that because it's a portable game that the gameplay hasn't been refined. I'm a fan of the addition of coins to pick up on the road. If you get hit or crash hard, you lose 2 coins. Lose all your coins and a little lightweight punk like Toad can knock you around! They've also weakened the lightning bolt attack. Nintendo has also added a simple single race mode so you don't have to go through an entire circuit to be able to race against the CPU and a nice replay mode too. The only change I don't like is that the bundles of bananas are gone.
One thing that hasn't changed is the classic control. It's really handy having the GBA's R shoulder button there. But for a Mario Kart 64 veteran such as myself, it may take a few races to get used to the D-pad after using the analog stick.
There's only one thing I'm slightly annoyed with and that is the sound. Mario Kart's music proves that GBA can pump out nice audio, it's just that the tunes themelves for the most part suck! A lot of the character voices are intact, but Wario now has a deeper voice (Booo!) and Toad doesn't scream at the top of his/her lungs when it gets blown up (that was sooo satisfying on N64). But the music was never all that hot in Mario Kart anyway. I like the Bowser's Castle music, that's just cool heh.