I would have to say Uncle Buck followed closely by Planes, Trains and Automobiles. I guess that is a little John Candy-centric. I don't think I have seen She's Having a Baby, but I like just about every movie he has ever directed.
All those are near and dear to my heart, but I've always enjoyed Uncle Buck. BTW a friend mine's wife was John Hughes secretary here in Chicago. Heard a lot of great stories and he seemed like a really nice guy.
I saw Breakfast Club so many times when I was in High school that 25 years later I could still probably watch it on mute and get most of the dialogue. Ferris Bueller a close second.
Wow. It's tough to choose. I think Breakfast Club (like Price, I watched it about a hundred times in H.S.) would be my number one, but I really like all of John Hughes's films that I've seen. Sixteen Candles, Pretty in Pink, and Ferris would probably all tie for a close second. Vacation, Uncle Buck, and P,T,&A tied for a close third.
#1 Breakfast Club - anyone who came of age in the 80s just gets this.
Ferris Bueller.
16 Candles. I still remember seeing this in the theater & laughing so hard my stomach hurt. Semi-interesting tidbit - I did meet a guy who was an extra in this as one of the geeks standing against the wall during the dance scene.