Best: Chinese in Chinatown, DimSum Chinatown
Best Chinese in Chinatown - Lao Sze Chuan ( www.laoszechuan.com ). I don't know about dim sum, though.
One noteworthy Chinese restaurant off Michigan Avenue is Shanghai Terrace ( http://chicago.peninsula.com/pch/dini... ). It is in the Peninsula, a luxury hotel. I had dinner there a few weeks ago. The food there was excellent, the service was impeccable, and the decor was quite luxurious. I wouldn't call it *better* than (or worse than) a more conventional Chinese restaurant, like Lao Sze Chuan; it's just *different*. Some people would probably be horrified at the prospect of paying $90/person (including very moderate alcohol and tax/tip) for Chinese food, but when you compare that against paying the same amount or more at many nicer contemporary American restaurants, it's not unreasonable in that perspective. (FWIW, I enjoyed it, I'm glad I tried it, but I probably wouldn't go back.)
There are other, moderately priced Chinese restaurants in the Michigan Avenue area. The two most popular are probably Ben Pao, a member of the Lettuce Entertain You restaurant group (pretty good, but no Lao Sze Chuan) and Big Bowl, a stir-fry place. Szechwan House is still around, too, but I haven't been there in years.
As for diners, the area around North Michigan Avenue is expensive real estate. I'm not even sure what corresponds to a "diner" in that area; diners are more of an East Coast phenomenon, one that you can sometimes find here, but generally in outlying city neighborhoods (e.g. Golden Nugget) and not so much downtown. You might have better luck considering the kinds of restaurants that are here, which tend to be a bit more specialized, rather than looking for a concept that predominates back in your home town but isn't nearly as common here. For example, unlike East Coast diners, Chicago places where a lot of people go for breakfast and lunch (e.g. Lou Mitchell's) often aren't open for dinner, and vice versa, and we tend not to have a lot of restaurants with enormous menus with many different kinds of food on them. Some, but nowhere near as many, particularly downtown.
As far as diners are concerned, the closest in the area is:
6 E Chestnut St
Chicago, IL 60611-2012
Phone: (312) 943-4373
It's very popular for breakfast and, since it's 24/7, with revelers staggering off of Rush street in the early morning hours.
You might also hear mention of Ed Debevic's. a tourist-central faux diner that I would never recommend to serious eaters, but kids seem to like the show.
I just had the best dimsum I've ever had in Chicago this past weekend at Shui Wah in Chinatown. They don't do carts, which means everything you order comes out to your table piping hot. If you're looking for good dimsum, this place is definitely worth trying!
Shui Wah (Chinatown Mall)
2162 S Archer Ave