Most of the lists here would make sense only if you were limiting the discussion to Hindi/Urdu language music.
You are doing a huge disrespect to singers who managed to make their mark even outside the comfort song of their native languages, while being the absolute best in theirs.
People like Yesudas, SPB , K.S Chitra and Lata and Asha to a smaller extend have managed that .
Among the present generation nobody holds a candle to Shreya Ghosal in that regard. She has won national awards singing in Bengali, Hindi and Marathi and has won numerous accolades singing in Tamil and Malayalam, two totally unrelated languages from Hindustani music belonging to a completely different language family. These two languages are traditionally considered the toughest to learn/sing in by northern singers and very few have made decent attempts.
She has songs in Malayalam, Tamil, Telugu, Kannada, Marathi, Gujarati, Bengali, Assamese, Nepali, Oriya, Bhojpuri, Punjabi, Urdu and Tulu ! Imagine the skill required to simply get the enunciation right in such diverse languages, let alone the ragaas and swars. Shreya Nails it in almost all of the languages, she's a freak talent.