A tiny sampler of some of his greatest pieces...
Piano Etude No. 6 "Autumn in Warsaw" (1985)
http://www.youtube.com/v/Ybr8S1hZvzQ
Ligeti - Lux Aeterna (1966) for 16 solo voices
http://www.youtube.com/v/lgRZnsAgKng
Lontano (1967) for orchestra
http://www.youtube.com/v/mtyaxDSYao8
Concerto for Piano & Orchestra (1985-88)
http://www.youtube.com/v/u31Yd3IUUrY