I watched many movies after came to US, mostly after 90s, though by my friend's words, the best Hollywood movies are in the 60s,70s, and 80s. I may start to watch those. But by far, I found many good movies are in 90s, and I listed some of those most impressive to me.

1. Matrix (1999) directed by Andy Wachowski, Lana Wachowski
What is real? What is existence? What is being?
I did not understand why Descartes' Cogito ergo sum (I think, therefore I am; 我思故我在) is philosophically a big deal, while this movie brings about the question.
http://www.imdb.com/title/tt0133093/

2. A.I. Artificial Intelligence (2001) directed Steven Spielberg
What is the meaning of to love, what is the meaning of life, and to live?
http://www.imdb.com/title/tt0212720/