I voted for Billy Wilder, but it was a tough call between him and Hitchcock.
The reason I voted for Wilder in the end is because he was so good at such a wide variety of films and film genres. Even if you include just the films on the shortlist above, you have:
Double Indemnity - Film Noir
Sunset Blvd. - Film Noir
Stalag 17 - War/POW movie
Witness for the Prosecution - Murder Mystery/Courtroom Drama
Some Like It Hot - One of the most hilarious comedies ever produced
The Apartment - Another great comedy
But he also won or was nominated for Oscars for such films as The Lost Weekend (drama), Sabrina (Romantic Comedy), Ball of Fire (Romantic Comedy), and Ace in the Hole (power of the press themed drama).
It's atually a very impressive filmography, when you look at all of his writing and directing credits.
Now, there is no doubt whatsoever that Hitchcock totally owns the suspense genre. He has so many brilliant classics it's hard to fathom - North By Northwest, Rear Window, Psycho, Vertigo, Rebecca, Notorious, The Birds...the list goes on and on. And he has some tremendous talents in his films - Cary Grant made 4 Hitchcock films that I can recall right off the bad...James Stewart also made 4. Grace Kelly and Kim Novak were regulars. Eva Marie Saint....Joan Fonatine...Sean Connery...even Laurence Olivier made a tremendous appearance in Rebecca.
BUT - as wonderful as all of these movies are, they ARE all of the same genre. Whereas Wilder seems to have mastered several genres.
I will say this though - It is interesting that John Ford is not on that list. I'd have thought he'd have more than 4 films on the 'must see' list. And that guy was really the first to make use of the whole 'sweeping vista' shots that the Academy so loves today in it's typical Best Picture nominations. I mean, right off the bat you have two of the three films that are widely considered to be the 3 best westerns ever made - Stagecoach and The Searchers (the third being High Noon). Plus John Ford has such films as My Darling Clementine, The Grapes of Wrath, and How Green Was My Valley to his credit, in addition to a host of other top John Wayne westerns like Fort Apache, She Tied a Yellow Ribbon, The Man Who Shot Liberty Valance, etc.