I perversely think Chongqing would be awesome: the most populous city on Earth, full of urban decay, horrendous planning... makes Gotham City look orderly by comparison. You could go out every day and evening, and never find everything therre is to see, do and eat.
But I hate the heat, so nothing doing for me.
There's the obvious: Shanghai. Might be a nice counterpoint to Beijing.
Most cities in Jiangsu and Zhejiang provinces are booming and wealthy: Suzhou, Hangzhou, Wuxi, Nanjing; smaller bergs like Changzhou are also pretty good for jobs, apartments, foreign goods and stuff to do.
Someone said something nice about Wuhan once. Too damn hot for me, but maybe it'd suit you.
Changchun gets strangely positive reviews, if that climate is more your style.
Fellow Saloonie Nate quite liked Tianjin.