I love Skynyrd's lyrics, don't get me wrong, but when it comes to singing? He was awesome but Mercury and imo, Elton took it to a different level. I agree also that Skynyrd's stuff connects more personally than most other bands I've listened to but if you want to get down to brass tacks, check out some of the stuff John Fogerty wrote. That man wrote some amazing stuff in a very short time with CCR.
John Fogerty doesn't hold a candle to Ronnie in my view. Ronnie had that soul feeling you could feel when he belted it out. Ronnie had more of a bluesy/rock kind of a voice. His younger brother has more of a metal/country voice.
