I find for my personal enjoyment I particularly enjoy songs with simple but meaningful chord changes and/or progressions.

That seems to put most of my favorites into the "Standards" catagory such as:

Dream
Stardust
September Song
I Remember You
Moonlight Becomes You
Moonglow
Stormy Weather
You Do Something to Me
Mood Indigo
St. Louis Blues
I Ain't Got Nobody

... to name a few

Tim