I'd say Saturday Night Fever for Travolta, and I'm 30. A person's age definitely plays a role in a topic like this though. I've noticed a trend among people younger than I am, that most won't go back and watch older movies or listen to older music. I'm not quite sure why that it or if it's something I'm imagining (I don't think so). Some actors, and even musicians, get a second life if they disappear and come back a while later. When that happens a lot of the younger crowd doesn't even know them from when they were first famous.
What's Robin Wright's? Winona Ryder? Ryan Reynolds? Matthew McConaughey? Neil Patrick Harris? Robert Downey Jr? etc., etc.
Everyone answer will largely depend upon when they were first introduced to each of them.