I'd say he's the best male rock singer of the 21st century (IMO). I've never heard anyone else with such a dynamic vocal range. Then again I'm a little biased since he's my favorite thing about the band lol
He's one of the best vocalists in rock music today. He was always a crooner before performing metal music, so that's harmed his range somewhat. You can tell by his early music in Grey Daze and even in DBS that he is just naturally a crooner but he had to change his voice for Linkin Park. I sometimes wish that he never started screaming because I do believe that it diminished his range and abilities to a certain degree. This is a person who grew up being influenced by Depeche Mode, the Beatles, Soundgarden, U2, and the Cure, rather than Slayer or Meshuggah. He trained himself to be a really good melodic singer rather than a screamer. When he started making metal influenced music with LP, it kind of took away from the great melodic voice that he was gifted with. But it was his own choice to better fit the sound of LP. It works on their albums but it really wears him down when the band is on tour. The overwhelming negativity some people have shown towards his singing is somewhat accurate. He is inconsistent live and struggles because his voice and muscles have to keep adjusting from screaming to belting to crooning. When he's away from touring for a few months and does a show after that resting period, you can hear the difference in his live singing. New Divide at Sonisphere 2009 and Let Down performance for the Hurricane Katrina benefit. He can still hold long notes and has power in his voice, even after being a smoker and abusing his voice by screaming (sorry, it's just a fact that this will gradually diminish your tone and range because it strains and tenses the vocal cords). I think still being able to sing like he did on "Waiting for the End", "Valentine's Day", "I'll Be Gone", and his side projects is kind of miracle.
I never really listened to Grey Daze more than, like, once over a decade ago so I didn't realise he sang in a totally different style to what he does for LP. His singing in Stone Temple Pilots (where the hell is the new STP stuff, anyway?) is noticeably different to me so maybe it's like that