There are many brands of already prepared Indian entrees that one can buy - at the supermarket, at Indian/Asian grocery stores, and even at convenience/gas stores operated by Asian owners.
One can buy frozen entrees or nonfrozen entrees sold in thin book- sized boxes requiring the contained bags being immersed in boiling water for 2 to 5 minutes (or microwaved if placed in a different container).
The best version of Baingan Bharta (roasted eggplant in tomato sauce and spices) I have had in the nonfrozen boxed containers is made by a brand called "Swad." Other brands like Ashoka have a more bitter taste and do not contain a rich mixture of onions and peas as does this brand. I find that adding fresh spinach to its Palak Paneer adds more body to it as it is much thinner than the Baingan Bharta in consistency. Although Swad labels their oil used as "vegetable oil" (I learned they use soy oil), there is little bitterness in the taste. Swad recently changed the packaging in which the entree is bagged. Its new bag allows the user to microwave the contents directly in the bag. All the other brands I have tried use a pouch that requires removal of the contents before microwaving.
The brand "Tasty Bite" has decent products and uses sunflower oil in its ingrendients.
As far as frozen brands go, I was relatively satisfied with the brand "Green Guru" which is the vegetarian line of the company called "Deep Foods." DF markets the same line of dishes under a different name and uses ingredients that are not as healthy. I have seen the Green Guru line sold only at Whole Foods. Other "natural supermarkets" would probably carry this line.
The brand "Ethnic Gourmet" is now sold at supermarkets. I found their packaging more appealing than their content. Not bad, but not spicy enough for me.
It will be interesting to hear of the quality and taste of other brands. Note that some brands have a taste that are more typical to a region of India, i.e. north vs. south. Your preference for the regional spice mixture will affect which brand you prefer.
Note that some of the boxed Indian entrees are very high in sodium. Some of the better brands offer products with a much lower amount of sodium. Most of the products I have bought require additions to make them more complete, such as adding a bit of yogurt with lemon juice and cucumber on the side to offset the heat from the dish. And of course, basmati rice and a small amount of fresh cilantro to make the dish more authentic!