I believe only the japanese restaurant in Epcot....has sushi right in the park.
We have enjoyed sushi at Cali grill and Wolfgang Puck's. I'm pretty sure there is a place in the dolphin that I heard has excellent sushi. I'm sure another dis-er will be able to help you out on the name of the restaurant.
All 4 restaurants in the Japan pavillion have sushi: Tempura Kiku, Teppanyaki, Matsunoma and Yakitori House. I've only been to Tempura Kiku, and the sushi I had was great. The Swan also has a sushi bar.
If you can get to DTD .......There was a huge selection of Sushi on the menu at Wolfgang Pucks. My 12yr old said it was the best he'd ever had. (how much sushi COULD a 12yr have had anyways...?) Noone else in the family likes sushi, so it's all I have to go on.