I'm a huge fan of Hitchcock's, Howard Hawks', Chaplin's, Frank Capra's and Billy Wilder's movies.
My top ten probably are:
1. The Big Sleep
2. Sunset Blvd.
3. Double Indemnity
4. Pandora's Box
5. Casablanca
6. Gone With The Wind
7. Blonde Venus
8. Lifeboat
9. Some Like it Hot
10. The Gold Rush

How about yours?

City Lights
Stairway to Heaven
The Ghost and Mrs. Muir
Double Indemnity
Roman Holiday
To Have and Have Not
The Thief of Baghdad
Gone With the Wind
Casablanca
Citizen Kane

...and pretty much anything with Abbott & Costello, Danny Kaye, Laurel & Hardy, and the brothers Marx. And Shirley Temple.

I haven't seen a lot of these in AGES, but when I'm in queue-building mode at Netflix, I'll start remembering a bunch I'd like to see again. This weekend: Funny Face.

Well, I have to admit, I'm quite a sucker for silent movies, as well as any of the old 'period dramas' from the 40s. My top ten would probably be...

1)The Killers - AMAZING 1946 Film Noir which has the original theme used in Dragnet. Sheer genius!
2) Double Indemnity - also awesome, although I read the book first, and it plays out a little differently...
3)The Wicked Lady.
4)Phantom of the Opera - the original Lon Chaney silent movie.
5)The Man Who Laughed - another silent, but absolutely brilliant!
6)Gaslight
7)Frankenstein
8)Cabinet of Doctor Caligari
9)Ghost and Mrs Muir - only time I'd call Rex Harrison a sex symbol...
10)North by Northwest

think it's hard to say 'what is old'

Buster Keaton Movies