greatest rock n roll front men.......

I'm almost like Moto on this one, in that I'll get back to you.

The great ones pop into my mind right away: Daultry, Plant, Jagger, Hendrix, Van Zandt, Tyler.

But the music I listen to can be so ecclectic at times that guys like Randy Owen, from Alabama, come to mind.
Or Gary LeVox, from Rascal Flatts,
or Danny Shirley from Confederate Railroad.
Darius Rucker, then and now.
Dave Matthews.
Mac Powell of Third Day. His voice and lead fit the band to perfection.
Toby Mac and Michael Tait fit the bill from DC Talk, and Michael Tait fronting his own heavy metal band is right on.
Mark Hall, from Casting Crowns.
You also have Chuck D from Public Enemy. Ice Cube brought such an edge to NWA. When they forced him out, they lost their edge.

Like I said, too many categories to narrow them all down.