I have seen that many people have chosen 3 Idiots due to it’s unique story focusing on societal and parental pressures in a humorous way. The film was very well done and I feel it is at least Aamir Khan’s best film. However, there are older films that are equal to it if not greater. I’ll list them out here:
Shree 420 (1955): This Raj Kapoor directed comedy starring him reflects how in order to be rich people must be willing to give up their ethics and how a poor man gets caught up in this world as well. He later realizes this is wrong
Naya Daur (1957): This film depicts the harsh reality of how people lost their jobs due to the industrial revolution. In the film a corrupt landlord pits machine against man to make them powerless until a brave young man makes a bet. He bets that his horse can race faster than a bus to a temple. If he wins then the landlord has to listen to the people. A moving performance from Dilip Kumar, one of the most famous method actors in Indian cinema
Mughal E Azam (1960): Yet another classic from Dilip Kumar, this is a visually stunning love story of a dancer and a prince
Guide (1965): This Dev Anand production starring him tells an emotional tale of a guide and his sad love story
Hare Rama Hare Krishna(1971): Yet another Dev Anand starrer this was a suspense thriller and an emotional tale of a brother trying to find his sister and bring her back from a dangerous hippie group
Amar Prem (1972): Perhaps Rajesh Khanna’s most meaningful film, this tells the story of a courtesan, a young boy, and a rich broken hearted man
Aandhi (1975): This film has such beautiful and mature performances from Sanjeev Kumar and Suchitra Sen that it can win best film ever based on that. A great story of how society cruelly treats a politician for her personal life
Deewaar (1975): One of the most groundbreaking films ever made in Indian cinema and the film that brought the “angry young man” phenomenon of Amitabh Bachchan, this intense and moving tale tells the story of two brtohers landing on the opposite sides of the law. Beautiful screenplay by Salim Javed and beautiful performances especially by the legend who no one can still match up till today Amitabh Bachchan
Trishul (1978): Another “angry young man” classic of Amitabh Bachchan, this tells the tale of a son taking revenge by destroying his estranged father’s business as the father dumped his mother just for this business. Beautiful screenplay by Salim-Javed, and brilliant performances from Sanjeev Kumar and Amitabh Bachchan
Muqaddar Ka Sikandar (1978): A big blockbuster during it’s time and yet a film that gets forgotten this Amitabh Bachchan classic tells the sacrificing story of an orphan
Shakti (1982): The most powerful tale of a father- son conflict remembered for the face off between legends Dilip Kumar and Amitabh Bachchan.
Sharaabi (1984): Yes Amitabh Bachchan has given Indian cinema it’s best films. This is a tale of an alocholic yearning for love over money
Nagina (1986): Mindblowing performance from Sridevi about a snake woman who is still devoted to her human husband
You have already mentioned the modern classics but these are the older ones more deserving to be called Indian cinema’s greatest film ever made
Romantic – Kal Ho Naa Ho
Thriller – A Wednesday/ Black Friday
Social Drama – 3 Idiots/ My Name Is Khan/ Rang De Basanti
Political Drama – Rajneeti
Comedy – Hera Pheri/ Andaz Apna Apna
Romantic Comedy – Dilwale Dulhaniya Le Jaayenge
Gangster/Underworld Movie – Once Upon A Time In Mumbai/ Satya/ Company/Gangs of Wasseypur
Best Revenge Drama – Baazigar
Best Family Drama – Kabhi Khushi Kabhi Gham
Best Psychological Thriller – Kaun?
Best Horror – Raat/ Bhoot/ 13B
Best science fiction – Mr. India
Best Biographical Drama – Bhaag Milkha Bhaag
Best sports movie – Chak De India/ Dangal
Best war film – Border