Xi'an Famous Foods is invading Manhattan, becoming an empire, and I better review them fast! I've actually never tried the one inside of Flushing Mall, but the basement Main Street location in Flushing has been a great place to fill yourself for $2.50 for quite some time. The lamb cumin "burger" (below) is one of the best deals in the city, and the $2 pork version is pretty tasty as well.
The noodles and soups at Xi'an are definitely above average as well, although more normally priced. The new East Village location offers a few places to sit and eat them, but doesn't have the character of the Flushing or Chinatown shops.
I think it will remain on-the-go food for me for some time.
Proof that the noodle soups are super fresh
41-28 Main Street (Basement #36), Flushing NY
Flushing Mall, Flushing NY
Chinatown, 88 East Broadway (door on Forsyth), New York NY
East Village, 81 St. Marks Place, New York