My choices are:

1)Paul Rodgers - Legendary Pipes, this guy is the prototype for Joe Lynn Turner
Lou Gramm and many others.

2) Glenn Hughes - His vocal ability is beyond human.

3) Freddie Mercury - Although he is gone He was the absolute best.

4) Ronnie James Dio- His voice is the heavy metal master, also the prototype
for that genre voice to compare to.

5) David Coverdale - His bluesy tone makes woman lustful.(My girlfriend says)

6) Robert Plant - In his day with the Zep nobody can touch him, also many
people copy his style.