Steve Perry, Freddie Mercury, The Best
Growing up, I didn't really listen to either of these singers. Why? Because all I heard was Led Zeppelin and Aerosmith. With a bit of J. Geils, Grand Funk, and whatever other bands my older brothers were listening to. Here is my point. In my older years, I can now hear what a great singer Steve Perry actually is. Period. In Rock. He reigns supreme in my book. I never got it. I was into hard rock, and Journey was polished and ballady. A friend once said to me (and she was a singer) that Steve Perry was the best rock singer ever. I fought her, saying Robert Plant was. I was wrong. Just wrong.
Freddie Mercury is also a fantastic singer. Not only is he a genius songwriter in my book and an incredible entertainer, but he takes the cake in the all-around category. Entertainer, singer, songwriter. Listen to him on the song "Under Pressure". His vocal range is vast, and his songwriting made Queen what they were.
So Steve Perry and Freddie Mercury are the best singers ever in rock and roll. IMO.
A nod to Steve Walsh of Kansas, too! Paul Rodgers also gets a big nod.