I feel like Lego Racers' ideas deserve a better implementation than they got. I haven't played the sequel, but at least in the first game there's no opponent AI and the way you build your car doesn't change anything.

I do know the second game gets rid of the really neat powerup system though. I liked the idea of picking up a base powerup and deciding to use it or wait until you've enhanced it to use it, though I guess if you can just continually warp maybe it's a little broken.