The first place that sprung to mind for me was Genji, at 40th and Spruce. Obviously, it's Japanese, and it's probably the best sushi I've had in Philadelphia. Which is surprising to me, since it's mostly students that live in the area.
Cooked dishes are also very good.
I think my favorite part is the setting - simple, and usually quiet. They have a second restaurant in Center City, but I've never been to that one. At 40th and Chestnut is Nan, which has been recommended by others on this board, but I've never been there. You might want to check below for that one. I have been there a couple times, and liked it, but I don't think I've had anything more elaborate than Pad Thai.