I think to classify something as the greatest of its genre it has to be groundbreaking and to a certain extent original. "ADA" by A R Rahman wasn't really either of these........not to say it's not a bloody brilliant album, classic act of ARR sound in fact, but it was nothing new from ARR either and there are better albums out there. But we all have opinions. Best doesn't mean favorite. If I should pick two songs from the album it would be Gulfisha & Mehrbaan.
Gulfisa Gulfisa
Tujhse hai mera gulsita
Aankhon mein tu raha
Palkon mein tu saja
Ashqko mein tu dala
Jab se mene likha sikha
Tera hi naam mene likha
Mujhse na door kabhi jana
Sunidhi Chauhan, shines throught the song. Sonu on the other hand does his job well but is overshadowed by the nightingales sweet voice. I think Hariharans would have been a better male choice with his brilliant vocals to support the pouring wine from Sunidhis voice.