Dude, that's a brutal request!!! that's like what's your favorite song - pretty broad question.
Something about the silver screen really gets me and I love Film Noir but couldn't name my favorite one though. Comedies from the 30's are special and I'm a big W.C. Fields fan.
For the 10 of thousands of modern lousy movies there are too many works of art to discount modern cinema - as rare as good work is it adds up over the years - couldn't begin to name all the quality films in all catagories - drama, comedy, etc. Of course a movie doesn't have to be high art to be a favorite - some of the worst films are so bad they're great.
P.S. It's A Gift ranks up there for me.