Navratna Restaurant is the oldest restaurant in Sec 17, Vashi, Navi Mumbai. Its a pure veg restaurant(No alcohol) and serves authentic south Indian, Punjabi and Chinese food.
I have been eating in this restaurant right from childhood and, trust me, I am never bored of it. The food here, especially south Indian and Punjabi is way too delicious and the best part is, it is hygienic.
For Non veg lovers, there is Sagar Restaurant(which is part of Navratna Restaurant) just above Navratna which serves decent Non Veg food.
Although lately it has become a little expensive, but its still worth the money. I think if you come to Vashi or are going to Pune/Goa via road, you should surely go to this restaurant.