I agree with Partha's list of talented actresses but would add Shabana Azmi and Kangana Ranaut to my list. Meenakshi Sheshadri (Shashikala) went to school with me – we were in the same class, different section, but she and I were in the same School House. She would get the House a lot of points during the inter-house competitions, with her dance performances, which she always won. She switched school after class VIII. And then years later I heard that she was crowned Miss India.
Coming to Alia Bhatt, I think she is a tiny bundle of talent. She is a brilliant performer. I rarely see movies but have seen 2 States and Udta Punjab and found her performance to be brilliant. No overacting or awkward moments.
"Further, in that film, she never looked like a traditional Tamil girl (I have read the original story of Chetan Bhagat)."
Movies are a different medium and directors when adapting a story, often take liberties with the storyline or the description of the character(s) to make the film commercially viable.
Moreover, the movie was not a character study of how a traditional Tamil girl should look. She must have played the character as per the script, and not the book. And a whole team works at creating the look of the character – she portrayed the character, the way the director wanted her to.
And it is her acting ability that is being discussed here, not her General Knowledge. If we were to base our preferences on character analysis then many would fail to make it to the list.
“You painted a naked woman because you enjoyed looking at her, put a mirror in her hand and you called the painting “Vanity,” thus morally condemning the woman whose nakedness you had depicted for your own pleasure.” - John Berger