Scorpion.
You're not the first person I've encountered who feels that, even if it's one of your favorite bands who plays one of your favorite types of music, that without a certain pomp to their stage performance they fail to completely amuse you.
Hey, that's you man. Nothing wrong with opinions.
But dude, even thinking of comparing Opeth to Ozzy seems preposterous. I don't give a damn if Black Sabbath were one of (if not the first) band who can be classified as 'metal', and that Tony Iommi opened certain doors riff-wise for many future metal bands. The fact still remains that Opeth is musically in a league of it's own, ESPECIALLY when compared to the style of Sabbath. That was the 70's, this is 2003. Following suit, the personality types of Ozzy and Mikael are completely different. Therefore, why SHOULD one expect the mild-mannered, soft spoken Akerfelt to step out of his own shoes and into those of another? I don't mean into Ozzy's shoes, but into those of a performer who uses frequent physical and verbal communication during and between songs. Mikael is who he is, and is obviously content within himself. If the band chooses to focus upon the creation of their music rather than the more transient facets of live performance (as I mentioned: facial expressions, body movement, the number of words spoken between songs), I personally see NO FAULT in that choice.
The fact that Opeth chooses to reserve themselves for what the concert is for (MUSIC), speaks louder in itself than any witty comment or random expulsion of words that Mikael could ever choose to utter.
I know that the initial post was your opinion, Scorpion, and I have no intention of stifling that. I just hope to shed some light upon what I believe is truly important when it comes to music.