When Harry Met Sally (1989)
This is easily the most quotable rom-com in history. "I'll have what she's having," is one of the most iconic scenes known to film nerds. Meg Ryan and Billy Crystal have this bizarre chemistry that truly works in this film as they are both neurotic and hopeless romantics.
It Happened One Night (1934)
Somehow, this film holds up better than the rest even after 80 years. The humor that the main leads convey is weirdly modern, which makes it more relatable than other classic films. A rich girl who feels smothered by her privileged life runs away with an unrestrained newspaperman and becomes his story... and his love interest.