This movie undoubtedly belongs to Rajkumar Hirani. He is an absolute genius for coming up with such a plot, witty dialogues, and an exceptional screenplay. I think the driving force of this movie was the combination of dialogues with humor along with entertaining scenes. The acting was superb by Aamir, Madhavan, and Sharman but it was the direction and the writing that works big time! The message is conveyed with perfection by Rajkumar Hirani and some scenes are executed in a very intelligent fashion.
