According to me:
Aneek
Amanat
Hemachnadra
Raja
Soumen
Aneek is far ahead from all the others.His voice quality,versatility and technical knowledge are his assests which keeps him much ahead from all of them.Amanat is a great singer too,but he is good in gazals mostly.Hemu has a powerful voice.Raja is good in sufi numbers.Soumen is good but not upto the mark.He is very introvert.he can't be called a package..i mean good singing with X factor.
So Aneek Dhar leads in all respects.And his perfs are improving in leaps and bounds.His voice is quite matured now.I have heard all his songs which he sang while anchoring saregamapa bangla.Aneek is great.:)