I have lived in DC for many years and have found some good places to eat. Here are some of my recommendations:

Best Asian: Cafe Asia

This place is downtown and has a really nice decor and great food. There is also one in Virginia that I have never been to and can't really vouch for. The restaurant is on 2 separate levels and almost has a nightclub feel to it. I usually ask to sit at the round tables on the lower level.

There is something pleasant about a round table and sitting with a group of friends. You get to all talk together rather than have separate conversations around a stale old rectangular table. There are great specials during happy hour including half price sushi and cheap asian beer.

I usaully wind up getting the terriyaki chicken dish. They recently raised the price but for a while, at less than 10 bucks, this was the best deal around.

I believe it is located around I and 18. It is a great place to bring out of town guests.

My runner-up for best Asian food would have to be Thai Chef in Dupont.