O'Tink, to come up with only one best-loved would be difficult...the Pachelbel Canon in D a definite contender...also Beethoven 5th Piano Concerto, and his 6th Symphony the Pastorale...
Since age 18, I have loved Domenico Scarlatti; JS Bach especially the Glenn Gould interpretations; Boccherini's famous minuet, but especially Night Music From The Streets of Madrid. And since you posted Mad Mary and her brother with their very special Ode to Joy, I have listened to that semi-daily!