I will have to concur with most of what Holly said about The Graduate. As stated, the movie Garden State outright copies many of the same themes of The Graduate; which after seeing the latter, I have much less respect for Garden State. What seems to differentiate the two films is that The Graduate is more of a universal film- almost everyone will understand the feeling of isolation, that the characters feel throughout the story. Hoffman and Bancroft play their roles wonderfully.

Also as Holly stated, this film was a product of its time, that is, of generational unrest and the destruction of traditional roles and institutions. To be honest, while believable, these themes come across as rather quaint upon viewing the film now. 

Overall, The Graduate defiantly deserves its spot on the list, as a modern classic!