For upscale near Yonge , check out Lai Toh Heen at Mount Pleasant and Eglinton
Chinese food though is all about the food, the service and decor should not be a factor. Some of the best food I've had in China are sold out of hole in the wall places where you had to share a table with other patrons and none of the chopsticks matched.
Lots of authentic places to choose from in Markham, Richmond Hill, upper Scarborough
Things to look for:
1) Regional specialty, a good chinese restaurant will specilize in one region's cuisine and not a mish mash of different styles.
2) Menu items, if you see silly things like "chicken balls", "sweet 'n sour pork" and "spring rolls"... leave. This is westernized chinese food.
3) People, if it's not packed with mostly Chinese diners screaming at one another... leave. Chinese people get very loud when they're enjoying good food. LOL