What song have you played the most?

Feels like Rain, John Hiatt. Close second, same song, Aaron Neville.

Great nominee @cmjones! Another one by John is "Lipstick Sunset", with a glorious guitar solo by Ry Cooder. When I saw the two perform the song live (as members of Little Village), time stood still. I had an out-of-body experience, like but not as transcendental as when I listen to J.S. Bach's Concerto for 4 Harpsichords And Orchestra. 

group wise because of the music and  sound quality - many others if not factoring in sound quality. alan parsons, csn, dire straights, dead can dance, depeche mode, eagles,fleetwood mac, elton john , carol king, pink floyd, little feat, joni mitchell, sarah mclachlan, tom petty, rem, sting, supertramp, till tuesday, neil young and i've missed many more.