Hmmm okay, rock is pretty broad, but I think I know what you mean.
Ummm metal first I guess
Just my personal thought... metal doesn't tend to rely on lyrics as heavily as other genres of music, so faulting a metal band for bad lyrics shouldn't really play a big part in your opinion on the band, at least not for me.
Best:
Jake Bannon (Converge) - I used to listen to Converge and not understand what the fuck this guy was saying, but I opened up the lyric booklet and read along with his incoherent screaming and it all made sense. His lyrics are like poetry about everything and anything this guy can think of. His outlook on love in Jane Doe is perfect.
Brent Hinds/Troy Sanders/Brann Dailor (Mastodon) - Who else could write lyrics based around Steven Hawkings black hole theories and czarist Russia?
Toby Driver (maudlin of the Well/solo projects) - I don't really like the guys bands, but theres no doubt he writes some good lyrics.
Michael Akerfeldt - Of course... this being an Opeth forum... but I really do enjoy most of his lyrics. I like the cryptic lyrics on Watershed, the concept driven lyrics on Still Life and Ghost Reveries, and certain songs with lyrics that are obviously deeply connected to the main himself (ie Burden, TNATSW, etc)
Worst:
James Hetfield (Metallica) - Later stuff of course. Pretty much goes without saying his lyrics are just dull and boring nowadays.
Chris Barnes (Cannibal Corpse) - Refer to: "I Cum Blood" nuff said.
Corey Taylor (Slipknot, Stone Sour) - Ugh.
Rock:
Maynard James Keenan (Tool, A Perfect Circle) - Always intelligible yet cryptic lyrics that always get me thinking. I love trying to pick apart what he is trying to say.
Jesse Lacey (Brand New) - This dude sings from the soul. All of his lyrics are filled with emotion, and thats how it should be.
Cedric Bixler-Zavala (The Mars Volta, At The Drive-In) - The craziest lyrics I have ever heard. I was playing "Vermicide" for one of my coworkers, when the lyric "We are sacrosanct" came up. He commented what a good word that was, and how its hard to use in normal conversation, and somehow he worked it into a song. His lyrics make no sense, but they are great somehow, at least to me.
Marilyn Manson - His lyrics are always clever and witty. The way he works his lyrics in the trypich is incredible. Staying with an overarching concept across three separate albums, while still getting all of his thoughts out into the lyrics is unbelievable.
Worst:
Maynard James Keenan (Puscifer) - Cuntry Boner
There are far too many bad lyricists in rock music to mention.
