If we're going to go instrumental classical and argue for the most perfect piece of music ever written, let's try Debussy's Claire deLune, Schiller's Ode to Joy, Beethoven's Fifth Symphony or even Holst's Mars Theme.
It also depends on what you mean by "perfect." Perfect for what? Elevator music? Funerals? Meditation? I absolutely fell in love with about the first 20 seconds of Fleetwood Mac's Everywhere when I first heard the "trilling" sound at the opening.
[youtube][/youtube]