Now that's a tough one!
For pure energy and showmanship, as well as powerful vocals, I'd go with Roger Daltrey and Mick Jagger. They both have a masterful stage presence.
For sheer vocal ability, I'd have to say that they don't get much better than Ian Gillan in his prime. He had an amazing range with a lot of control, and timbre in his voice. He was hired to sing the role of Jesus on the rock album JC Superstar. They offered him the stage role, but he declined since he was ready to go on tour with Deep Purple. He also had those remarkable high note banshee screams that were on pitch and with vibrato, at times. Sadly, that voice gave way too early in his career. He seemed to have a lot of respiratory problems, was known to smoke a lot, and those screams do take a toll on the vocal chords. (He writes about it in his autobiography).
I will also put Klaus Meine on this list. This band has always had a lot of energy, and Klaus can sing those great power ballads, as well as the hard hitting rock songs. He also has a good range, even now.
All four are still active. I won't bother to rank them. They are all great.
"Music can change the world because it can change people." - Bono
