There are so many places to eat in Chinatown, but I have definitely found a favorite Shanghainese place- Evergreen Shanghai (also known as Shanghai Garden) at 63 Mott Street. My usual order is the crabmeat and pork juicy buns (SO GOOD) and mixed meat and shrimp with shanghai lo mein. For $12, you easily feed two people.
The service is so-so and it ain't pretty...but if you are solely focused on food, try this place. There are several hundred options on the menu if you don't like my choices above.