So many good ones
Vertigo
Rear Window
Psycho
Rope
Spellbound
North by North West
The Man Who Knew Too Much (1956 version)
The Thirty Nine Steps
Strangers on a Train
Rebecca
The Lady Vanishes
Marnie
Suspicion
The Saboteur
To Catch a Thief
I'd recommend all of those (favourites in bold), and most ahead of the much overrated The Birds.
I have to say, I don't like either Psycho or The Birds as much as his other classics, and they seem to have overtaken people's perceptions of Hitchcock (the way a band might have a couple of massive hit singles that aren't entirely representative of the rest of their material). But they are both hugely influential films and good examples of how goddamn talented Hitchcock was