Maybe it's a cliche, but I love Glen Gould's interpretations of Bach's Goldberg Variations. I saw another very, very good performance of this by a young Finnish pianist, Olli Mustonen. If you get a chance to hear (and see) him perform, you should.
Satie, Debussy, Ravel, Rachmaninov - all wonderful too.
And one of the most sublime moments of my life was hearing a completely mad but awesomely talented friend of mine playing one of Chopin's Nocturnes in a completely deserted chapel in one of the Oxford colleges... it was, as Gary says, a justification in itself for the existence of humanity.