The quality or locale of a restaurant shouldn't change the percentage of the tip, since naturally that will reflect in the bill that the percentage is taken out of. It's not like an upscale Manhatten waitress will be making the same amount as a New Jersey IHOP waitress just because they both get tipped the same percentage.
The level of the tip is dependent upon the culture. In NYC, particularly Manhattan, 15-20% is fairly standard. In other locales, I've seen 10% as acceptable. It really depends upon where you live (or dine). And, of course, in many European countries the assumption is that the tip is built into the check. They're not all cheap folks, necessarily, they're just not used to tipping. I went to school in the early sixties in Southern Ohio. No one tipped. It wasn't expected. The waiters, bartenders, etc. all worked on salary.