Like others the Stadium line would probably be my no.1 line but a close 2nd is definitely the Sportsman line. I love this line for its graphic pieces that are inspired by Hunting/Fishing magazine covers from the 1930's/40's:
I also love these 'Outdoorsman' shirts (although I'm not sure if they were part of the 'Sportsman' line?):
The reason I love RL is that it captures a sense of Americana perfectly. Ralph was from a poor immigrant family who lived in the bronx, but the classic American lifestyle and the imagery that went with it was very clear to Ralph it seems. He knew how to take this imagery, put his own spin on it and make it his own. That is how alot of great art is made, and Ralphs Best pieces are great pieces of art in my opinion.
The New York subcultures that formed around Polo in the late 80s and 90s are fascinating to me because they also took this idea of taking something that wasnt meant for them (expensive clothing, that was aimed at rich preppy kids at the time) and using it to create their own unique style. This culture felt very organic though and not forced like modern day fashion trends are.
90% of the brands items are pretty mediocre in my opinion. However, the pieces represented in that 10% niche really hit that perfect spot between 'Cheesiness' and classic design. Much like Pop Art does. Stuff like the 92 Ski graphic definitely makes me think of Roy Lichtenstein.