I'm with scott on why revelations sucked. He just can't hit the notes he used to and it seems like he's desperately trying to. Granted, he's got a great voice still but he needs to learn how to compensate for his lack of range by sticking with the baritone singing. Audioslave's "Like a Stone" is a perfect example of his hoarseness sounding great.
In the Soundgarden era, he could fucking belt it out. He could hit notes like an opera singer, falsetto and even at a full scream. "Smokestack Lightning," "Slaves and Bulldozers," "Jesus Christ Pose," "Mind Riot," "Say Hello 2 Heaven," are good examples of how ridiculous his range used to be. "Cold Bitch" is another great example of this, which is actually a B side. It's a fucking awesome song as well, so definitely check it out if you haven't.
He's probably my favorite singer and his range is partly why -- when it sounds good, that is. Without the range he used to have, I'd still say he's my favorite when he can pull it off. "The Last Remaining Light" from the Audioslave S/T is one of his best vocal performances ever, if you ask me. The contrast between Revelations and that older stuff is proof that he's losing his voice badly, but if he can control it like he did in Out of Exile or the S/T Audioslave, then he's definitely still got a solid set of pipes.
So anyway I happened to start looking up some Soundgarden lyrics and just reading them. We're talking songs I've listened to a thousand times and loved forever. And I discovered just how damn dark they are! Like "Burden In My Hand" sounds like a good little song but if you read or hear and understand the lyrics you are just like "Holy shit! That is dark and morbid as hell!!!" I just found that interesting.
I personally like listening to the lyrics in a song, so I like to look them up. Some of his lyrics suck, but at the same time, some songs just have fucking great lyrics. I thought "Burden in my Hand" had great lyrics, and "Limo Wreck" is another that comes to mind right away. "Like a Stone" is also a great one. Seems like his darker lyrics are the best ones though. Revelations had no redeeming lyrics whatsoever -- everything was poppy and lame. Half the time, it seemed like he was writing lines just to rhyme them with the previous one.
EDIT: Also, as you may be able to tell from my icon, Badmotorfinger is my favorite Soundgarden album. I suggest listening to it a few times, because it's a little different than their other stuff and it took me some getting used to. I just love how heavy it is, though, and a few of the songs give off almost a tool-esque sound ("Slaves and Bulldozers" particularly). Cornell's voice is in top form on this one, too. Superunknown is a very close second, though. How can you not love that album? On a related note, I also have a badass version of New Damage with Brian May of Queen on guitar.