progressive metal

for some extremely sweet instrumental progressive metal check out canvas solaris, any of the derek shininain albums, or on the virg which is soooo bad ass.
 
Green Carnation - Light of Day, Day of Darkness is a good Prog metal album.
Porcupine Tree
Anekdoten (not really metal but still good)
Augury
 
When I recommended them I wasn't even thinking about them not being metal. My bad. They're really ambient prog rock, not metal.

Anyway, I think their vocalist kicks ass.
 
I listened to a couple of their songs and there wasn't one Metal moment.
Probably because you listened to the "wrong" songs. Their debut album "Life Cycle" definitely is metal - in the vein of Watchtower's "Control And Resistance". I'd also say that at least some songs on their fourth album "Sophisticated" could be classified as metal.

And their vocalist is bland.
It's the fourth one in their career. You'll have to find out for yourself if you like any of his predecessors better.

Two of my favourite progressive metal albums are "Terrestrials" and "Orgasm" by Atrox.

np: Détente - "Holy War"
 
Best prog-metal band ever: Ayreon/Pain of Salvation


Worst one: I would say Dream Theatre... some are probably worst but I don't know them...
 
Even i find DT kinda boring now. Definitely not the worst but boring.
I did like them to begin with(still do like some of their stuff), but they haven't progressed much at all. It just gets bland and boring after sometime. I mean, they have one of the best guitarist, drummer & bassist. They can pretty much play anything if they wanted to...It's just sad to see very less progression over the years. They have been around for quite a while now...cmon, they can atleast change it up a bit.

Anyways, I'd consider Pain of Salvation to be the best.
Truly progressive. I liked everything from 'Entropia' to 'Be'.
Quite a few fans hated 'Be' but i would consider it one of their best. The live DVD version is especially awesome. And oh, there's no point in listening to them without checking out their lyrics. I know few ppl who listen to DT/Symphony-X are in it just for the instrumental masturbation.(I try to make it a point to check out the lyrics also, even on first listen)
 
Dream Theater is one of the greatest bands of all time, and anyone who thinks otherwise is clearly insane. I see a lot of progression throughout their career.

Other good prog. metal bands would be Pagan's Mind, Pain of Salvation, Porcupine Tree, Evergrey, Shadow Gallery and Vanden Plas. Those are the once I listen to most often anyway.
 
I will throw out two of my favorites: Seventh Wonder - Waiting in the Wings & Subterranean Masquerade - Suspended Animation Dream

As for the best/worst, progressive metal is way too tricky a subject to have this debate.