well, when i was introduced to metal, i was introduced to it in a MUCH different way than most metal fans. where most people were introduced to stuff like iron maiden, metallica, pantera and megadeth, i was listening to stuff like Haggard, therion, theatre of tragedy, the gathering, shape of despair, the sins of thy beloved, tristania, bathory and bunch of other gothic/symphonic/atmospheric/classical bands that had an immense atmosphere to them. and at the same time, they were doing dual vocals as well along with other instrument arrangements. from guitars that were mainly power chords just to create rhythm, and their solos were very basic and far from shredding. they used classical instruments for solos if need be. their vocals were seamless in terms of transition. from clean operatic male/female vocals-almost angelic, they switched to growling and demonic vocals.
and then when i was introduced to opeth, i didnt really see what others saw. sure, i found that unique that mikael(or how ever you spell his name) is the only vocalist being able to do both vocals. thats something i hardly ever see, but opeth isnt really pioneers in that.
as for opeths first few albums, i've heard of most of em from beginning to end, and have given em a few listens each, and still i say taht each album only had like one or two songs that kinda tickled my interest, but nothing really. and i still say that their song 'the grand conjuration' is the song that stays in my memory as their most different song from all their others. and even then, people seem to say that the opening riff is something epic and amazing and highly memorable and all that...i dont really see that to be honest. its just a normal riff that isnt really all too amazing.
yes, i do give opeth that they change their time signatures around mid riff/solos, and their progression in songs is pretty cool...but thats pretty much it...
Fair enough, but Opeth was not a popular band until BWP. The other bands you mentioned were much bigger. i got into metal the "typical" way (metallica, megadeth, slayer, then on to the 80's shred thing, then on to dream theater, then onto extreme metal), but at the point i'd heard Opeth, i'd also heard a lot of those gothic/symphonic kinds of bands. Those bands to me were predictable. No interesting chords, no interesting chord changes... Opeth was like the antithesis of this. I couldn't give a rats ass that mikael is the same guy doing growls and cleans, as i'm into music for the sound. not the mechanics or the "difficulty". I can listen to MAYH still and get chills, nearly 10 years later. The way that album tells a story and develops is not like any others, and certainly not like any others at all at the time (excluding Crimson by EoS).
I'm also a "transition" guy. I strongly believe the notion that the best parts of music are not found in individual parts in and of themselves, but in the connection between a certain part and what came before. Those are the moments i get chills, and i don't think it would feel the same without being put in the "place" the previous section puts you. This was something that Opeth seemed to understand and employ all the time. MAYH has so many epic endings to the songs. The end of April Ethereal (i don't know how or why, and i'll... never... know WHENNNNN), the ending of When (...AND I CRIEEEDDD), the ending of Demon Of The Fall (just one second... and i was left with nothing), etc. etc. etc. I also don't typically listen to songs alone, for this very reason. I enjoy album architecture and treat it all as a whole. Same concept on a larger scale. I have an entire project that i've been working with for about 6 years now that is only based on album architecture and creating shifting atmospheres. I don't even use my own music for it!
Anyway i am getting off track. Opeth may not be for you, but there was nary a person in the late 90's who knew of Opeth who didn't think they were one of the shining gems of metal. As things become popular, people lash back, find faults of their own, etc. and while Opeth has gotten weaker since then, in the context the first 5 albums were released, no one could touch them, and no one knew how to sound like them.