I found the sushi at Aikou to be very good. I have not been impressed by other menu items but I've read some recent, positive comments so I need to make a return visit to this restaurant.
Domo 7 in Whitehouse Station (Route 22E, same strip mall as McDonald's) was very good when I tried it about a year ago. Friends who have been more recently also liked it.
A couple of people on the board have recommended Shiki on Route 31 but I've never been.
For the best sushi, however, I suggest you leave Hunterdon County and drive to Shumi in Somerville. It has some of the best sushi outside of Japan. Shumi has been discussed quite a bit on the board so if you're interested just do a search.
I couldn't find a web site for Shiki but here are the ones for Aikou and Domo 7:
I was in Clinton with a friend this afternoon and we walked by Wasabi, a sushi place on Main Street. I have never been but she has.
She said it's fairly good but some people are disappointed to discover that it's strictly a sushi restaurant and doesn't serve everything Japanese. Seems to me that if it has survived by serving only sushi it might be a find.