I have friends who tell me that it is really a challenge to find some good Asian or Japanese restaurants in Paris. I think this would be because of the very little influence of Asian culture with the French culture. And they also told me that if you really want some decent sushi, you will have to shelf out few cash. Two of the best sushi restaurants that they recommended are Isse and Isame. They both serve delicious sushi, but Isami is relatively cheaper than Isse. Hope that helps!