When it comes to Thamizh songs, my all time favorite is Sethalapathi Balasubramaniam, a direct disciple of Papanasam Sivan. He is one of the few singers who always placed a composition's bhaavam and bhakthi over it's technicality. Sadly, he isn't all that popular and never received the recognition he should've got.
An article from The Hindu on SB.
Some of his songs:
http://myblogkumara.blogspot.com/201...ers-place.html
http://www.gaanam.net/forums/showthr...-vintage-music