Blade Runner, Alien, The Great Race, The Court Jester, Those Magnificent Men in Their Flying Machines, The Three Musketeers (with Gene Kelly), Assault on Precinct 13 (1976), The Thin Man, Ninotchka, To Be or Not to Be (1942), Heaven Can Wait (1943), The Public Enemy, The Seven Samurai, The Philadelphia Story, Singin' in the Rain, The Band Wagon, Steamboat Bill Jr.,The General, The Adventures of Robin Hood (1938), Reservoir Dogs, Pulp Fiction, Jackie Brown, Bonnie & Clyde, American Grafitti, Star Wars, Bringing Up Baby, La Nuit Américaine/Day For Night, Spartacus, The Graduate, Taxi Driver, Raging Bull, The Silence of the Lambs, The Sting, Butch Cassidy and the Sundance Kid, One Flew Over the Cuckoo's Nest, The Fabulous Baker Boys, Crouching Tiger/Hidden Dragon, Some Like It Hot, One Two Three, A Fish Called Wanda, Do the Right Thing, The French Lieutenant's Woman, Apocalypse Now, 2001, Dr. Strangelove, M*A*S*H, Hana-Bi, To Catch a Thief, Rear Window, Vertigo, North by Northwest, His Girl Friday, Citizen Kane, Miller's Crossing, Fargo, Who Framed Roger Rabbit?, Annie Hall, Manhattan, Radio Days, Charade, To Kill a Mockingbird, The Fearless Vampire Killers, Charley Varrick, All the President's Men, The Princess Bride, Once Upon a Time in America, The Lord of the Rings: The Fellowship of the Rings, Monsters Inc., The Godfather, The Godfather Part II, 1900, Il Gattopardo/The Leopard, The Getaway (1972), Bullitt, The French Connection, Chinatown, Tron, The Great Dictator, The Gold Rush, Monkey Business, A Night at the Opera.
(No, I didn't type them. I copied them from a list of my DVD collection. Lots of other favourites are missing - especially other old movies and the European ones.)
Best out of those: I don't care, love them all.
Most favourite: No idea, it changes daily.
Most often watched: Butch Cassidy and the Sundance Kid (I think). Probably because imo it's the best written, most elegantly directed buddy movie ever created with one of the best movie scores ever composed - plus: Newman & Redford.