Do your research, I'd love to see a better one, but I think you will find they are all worse.
So9
Any legal system is only going to be as good as the people who administer it.
We have a good number of bad apples in our judicial ranks, of this I am sure.
From my observation, I would say that the Japanese judicial system is a good one (but by no means perfect, and in fact it is presently undergoing some modification), but it and Japanese society are too different from our own for me to make easy comparison.
For easier comparison, I would think Australia, Canada, and the UK would be the most natural. I personally am not a fan of Napoleonic systems and in my opinion that they are clearly worse than our own.