On foodie discussion websites, there's usually a post by someone complaining that an 'ethnic' restaurant he/she visited (mostly in the United States) is not 'authentic'. As someone who eats out a lot, I have problems with that word. Authenticity is impossible to pin down when you are talking about national cuisines.
Take, for instance, Chinese food. The Chinese cuisines we find in Hong Kong, Shanghai and Beijing are all distinct but we can appreciate them for their differences. Hong Kong cuisine is known for having light, clean flavours that highlight the best ingredients. Compare that to food you find in places with large numbers of Chinese immigrants and you'll find some of the dishes are Chinese in name only. But if you eat them with an open mind, they can be delicious in their own way. The 'natives' might call it Chinese but it would be more precise to call it Chinese-American, Chinese-Indian, Chinese-Trinidadian and so on.
In the past, Chinese immigrants didn't have access to the ingredients they were used to on the mainland or in Hong Kong, so they made do with whatever was available. They tried to keep the familiar flavours but also learned to adapt so the food would be palatable to others. Chinese-American food has distinctive dishes, such as huge, fat egg rolls stuffed with bean sprouts, carrots and mushrooms; and chow mein, the ingredients of which are cooked in batches then left to sit under heat lamps, making the noodles, meat and vegetables overcooked and soggy.
Chinese food in India tends to have a lot more sauce and is spicier than the regional cuisines of China. It's not the same type of spiciness found in Hunan and Sichuan cuisines but it has flavours that please the Indian palate. But it's not anything that someone from Hong Kong or the mainland would recognise from home. However, it's 'authentic' Chinese-Indian food - and that doesn't make it wrong, just different.
The only 'bad' food is something that's incorrectly cooked. In Shanghai, xiao long bao is served at lots of places - all are 'authentic' but some are delicious (thin but resilient wrappers that contain a good amount of broth and meat) while others are not.