In hindi playback there are always the great's like Kishore, Rafi,Hemant Kumar and I absoluetly adore their singing. However , I feel that Amit Kumar(son of Kishore da) is a brilliant singer too. Really unfortunate that he didnt really do as well as he deserved, but some of songs in the movies from 80's , especially under RD Burmans music direction are superb !
Amongst western singers, I really like Bob Dylan and Bono(from U2). They really have brilliant voices!
Amongst the newer lot, I am a total fan of Sanu, KK and of late Kunal Ganjawala(Sang O humdum from Saathiya.....and Bheege Hoth Tere from murder).