There have been a few worthy contenders to Mario Kart's throne as king of the kart racer, most notably Diddy Kong Racing and Crash Team Racing. A title which is slightly less renowned but just as good in my opinion is Wacky Races on the Dreamcast. I must point out that while a Wacky Races came was released on a number of formats, it was quite a different game on most of them (PS1, GBA) and should be avoided. The Dreamcast version (and its PS2 port) is the one worth looking at.
Borrowing quite heavily from the structure of both the aforementioned racers, Wacky Races puts you in a open world environment with various sub levels that you can drive up to and enter various challenges, which are unlocked by earning stars from earlier, easier challenges. You will begin with straightforward races around the many colourful tracks which aren't too challenging. Periodically you will have a boss race against another character such as Professor Pat Pending in his convert-a-car, and you will unlock them as playable characters if you manage to complete all of their challenges. Then comes the Wacky Championship, which is all of the races in a particular environment back to back (5 races in all). After that you have to complete the Golden Muttley challenges, which is somewhat harder but doable with a bit of practice and skill. It's basically the same as the red coin challenges in Diddy Kong Racing, where you have to collect 10 objects scattered around the track as well as finishing in first place.
There's more to come... Battle Arena challenges are what they sound like, destruction derby style events where you have to shoot the other characters with your weapons until you are the victor. Finally you have the Team 00 challenge, which is four elimination races (you lose, you're out) followed by a rather tough face off against Dastardly and Muttley. These can be challenging and frustrating but if there's one thing you can say for this game, it isn't short of things to do.
Each character has their own set of weapons but they can all be divided up into certain types, such as defensive shields, offensive weapons and speed boosts. You start with three abilities and three face buttons to map them onto, but as you progress you will earn more and will have to choose which are the most useful. Graphically and audibly the game is still very impressive today, with bright, cell-shaded graphics that mimic the look of the old cartoon perfectly. The voice actors sound just like the people who did the original voices, but I'm not sure whether they've actually sampled the old cartoons, got the original voice actors to come in and record new lines, or managed to find new people who can do very good impressions. Whatever they did, it works.
Throw in split screen multiplayer and a simple arcade mode if you don't fancy getting into the championship mode and you have a lot to see and do. I had great fun playing this game and picked it up extremely cheaply too. Give it a spin!