You can Vote for Most Valuable Lead Vocals (Rock Groups)

Chris Cornell , Eddie Vedder, Delores ORiordan Dennis Deyoung
Rod Stewart, Eric Burdon,SRV, Just to name several greats others on this page have already been mentioned .

Every rock band whose overall sound is essentially defined by their lead vocalist.  The list is endless.

Roger Daltrey of the Who

Hi, map.
Morrissey was the lead singer of The Smiths.
The Smiths simply would not be The Smiths without Morrissey, no substitute.
No Morrissey, no Smiths.
He also wrote or co wrote their songs. 
Unique voice, unique lyrics, unique sound.

It’s true lead singers are key to a group’s success.

The MVP though plays a key role in elevating that group above others in other words the value can be measured by overall success. So a guy like Mick Jagger would qualify in that they are a very successful band. What if the singer was not Mick? Mick is not a great singer. Would the stones have been better off with a better singer? Probably not because Mick also played a major role on writing their songs. So an MVP despite not being a great technical singer. In fact I often think the Stones would be better served live with a better singer because Mick’s live performances though entertaining have often been very ragged and inconsistent vocally IMHO.