i cant believe the original ones are as noisy
Oh, I can: try reading the raw values from an analog joystick. It's surprising that anyone can use a flight simulator program without crashing on take-off 
Have you tried adding some software filtering? I've had good results in some resource-constrained micros with a simple weighted moving average, done by adding the latest value to the previous value and dividing by 2. This gives you a sum of (1/2 reading[n]) + (1/4 reading[n-1]) + (1//8 reading[n-2]) ...
This does well on signals where there's a lot of small-amplitude "jitter", but not much drastic change in the "true" signal between samples.
Have you opened up the nunchuk to see what's inside? I suspect it's mostly empty, with only a small PCB that you could mount to your car a lot more solidly than the whole nunchuk.
Ran