As this thread is already punned out, all I can add is that most Chinese, Japanese, Thai, Indian, Vietnamese restaurants have some vegetarian dishes (or will make upon request), so it is pretty easy to find a good vegetarian restaurant anywhere in the world.

As for vegetarian restaurants worth seeking out, I know of 3 (as I am not vegetarian I don't go seeking them out). The last 2 have non-vegetarian dishes on the menu, but their best dishes happen to be vegetarian.

1. Greens in San Francisco. Pretty famous, so needs no introduction http://www.greensrestaurant.com/
2. Joel Palmer House in rural Oregon (50 miles from PDX) specializing in mushrooms and morels (many home foraged)http://www.joelpalmerhouse.com/Scripts/aboutus.asp
3. Shaan in Rockefeller Center NYC. Good indian food http://www.shaanofindia.com/aboutus.htm