Eh, call me impatient as I'm about to list a few other classics now... actually it's more about having the time to do so and trying to put down some choices while I think about them.
Here's goes a few from my list:
An Affair to Remember. Sappy, sweet, probably leans a bit more to the feminine side, but a great film with one of my favorite stars in it. I could watch it over and over again and never tire of it.
It's a Wonderful Life. Again sappy and sweet, but with a great message. Again one of my all-time favorite stars in it (actually more than one of my favorites from the golden age). While there was a period when I was a bit worn down from the insane number of airings that would happen around the holiday period that was rectified fairly quickly and now we get just a few showings a year.
North by Northwest. Detecting a pattern with the favorite film stars? Well this one had one of my favorite directors as well. You could name just about any Hitchcock film and I'd concur that it was classic. This one just hits all the right notes for me.
That's 3, plus the aforementioned 12 Angry Men, for a total of 4. There's a bunch of others that I could list (The Sting, One Flew Over the Cuckoo's Nest (which I just got the collector's edition of on Blu-ray), Where Eagles Dare, Stalag 17, Arsenic and Old Lace and several others) that make it tough to choose an actual top 5 or top 10. Realizing of course that I've not mentioned films with stars like John Wayne (where I'd have a difficult time choosing which film to list).