In DC proper, I think Loeb's deli is as a close as we come to a real NY style deli. After 51 years at 15th & H, NW, it closed in September but is scheduled to reopen next month at 17th & I.
Does anyone remember Stacks, Jack Abramoff's horrible kosher deli in the old Washington Star building Pennsylvania Avenue? It attracted lots of customers from the Holocaust Museum but did not last long. Now it's home to the DC branch of Fogo de Chao.
For a better memory, I miss the old Shirlington Deli. Surly service, kosher pickles on the table - it was great! When Shirlington was redeveloped it briefly moved to Jeff Davis Highway but did not last very long.