The best Chinese food in the City: Our Place Shanghai Tea Garden. 55th between 3rd and Lex. (Shanghainese style)
The best Chinese food in C-Town: Ping's. Mott Street between Canal and Bayard. (Cantonese style)
I personally don't like Wu Liang Ye. Gu Xiang Wei on 55th and 2nd has some good choices and by far is the cheapest among all the ones that I would recommend. It is a little bit off and the service is quite poor.