No question Charlestown has some of the best creamy chowders you'll ever taste.
But never mind that, IMHO their most important feature is that is it -very- family friendly. They sponsor coloring contests for the kids, willingly divide adult entrees, and kids eat free from the kids dinner menu every weeknight. My husband and I routinely go in there for a dinner and a split of the table red and get out under $30 for a family of five.
Good quality diner food, very good service, and reasonable prices. Plus the best chowder in Seattle.