It's more than just his voice though. His charisma as a frontman as well as just his sly vocal style really gave him all that recognition. There wasn't really anyone like that before Plant. JLB's vocals may have gotten more recognition in that time but I don't think he would've been elevated to Robert Plant status.
Probably not the place for it, but I really don't think Plant gets his due, and I don't know if that is because Zeppelin is so ubiquitous, or because his solo stuff wasn't as iconic, or because there just isn't type of concert like the ones Zeppelin used to put on.
But I went through a pretty big Zeppelin kick a couple months ago and broke out the DVD and TSRTS, and man, Plant was a rock GOD. I also saw a couple shows on the Page/Plant tour, and there was a moment during... I think it was "Calling To You", where they broke the song down and did some interpolations (like they used to do in Dazed and Confused). And at one point he was sort of mumbling/scatting Break On Through by the Doors, and it was pretty cool, lights were low, it was really... vibey, if that's a word, then he moved into "For What It's Worth" by the Buffalo Springfield, and when it got to the "chorus", the lights flashed on and he belted out "Stop! Hey! What's that sound everybody look what's goin' down!" and it literally took my breath away. (Of course the band did it again later during "The Song Remains The Same", to this day the single greatest moment I've ever had at a rock concert and I've been to a few).
Oh yea I agree, I like his aggressive vocals a lot, just wish he'd mix it up more these days like he did on Odyssey. But yea, Russel is one of my all time favorite vocalists for sure, so I definitely agree there. If there's ever a more modern singer who deserves to be up there with the likes of Dickinson and Halford, I think it's Allen.
Am I in the minority in that I don't really care for Russell Allen's singing? More specifically, it isn't BAD, he certainly has range and control of his voice, but I don't know, what I've heard? He's not Dickinson or Halford. Or, in my book, LaBrie. Caveat, I am not 100% conversant in the Symphony X catalogue.