Exclusive

"I'll be back" ... "You can't handle the truth" ... "Dude, where's my car?" ... some of the best movie lines in the history of cinema -- but Aaron Sorkin says the #1 quote is straight out of the '70s.

Sorkin -- the Academy Award-winning screenwriter of "The Social Network" ... and the guy who penned "A Few Good Men"  ... was leaving the Chateau Marmont yesterday when our photog dropped the "best line ever" question on him.

Check out the clip for his answer ... but, we'll give you a clue -- here fishy fishy!