Meh, I figured you would mention those guys. Nothing really particularly special about any of them.
I actually was listening to the radio the other day (shocking, I know) and a song came on and it sounded exactly like Stapp singing it and I was confused. I was like "Did I totally miss a song off his album?". Turns out the song was by 3 Doors Down. Stapp sounds like everyone else. Of course YOU can differentiate him... you listen to his songs all the time for a long time. I can pick him out. I have listened to his songs often. But he still sounds very generic.