Ok, here's my 2 cents.. No.
There are no other bands that even remotely resemble Opeth in all those magnificent characteristics that make Opeth what it is.
I was never into death metal at all before discovering Opeth and since then (about 2.5 years) I've looked and listened to more death metal bands than you can shake a stick at and I have met with nothing but disappointment in that venture. All the other bands that I've been told fall into the same 'catgory' as Opeth I've found quite lacking in the beauty/emotion/silky smoothness that I've come to love about Opeth and I've found much of it kinda or very amateur in comparison, particularly the vocals. I've even listened to death bands that Mikael himself likes and thought the same thing.
Opeth are truly in a class by themselves with vocals, musicianship, and ideas that are light years ahead of everything else I've heard, imo. Of course, it should be noted that I'm quite musically anal and it takes a hell of a lot to impress me, hehe. Groups that I've heard that didn't make me want to puke that I was able to appreciate for their chops and originality are Eventide, Cynic, and Arcturus, but still these are nothing compared to Opeth, imo (of course, who's opinion do you think I'm talking about, hehe).
Aside from this, I don't think it's very fair to the other bands to be compared to Opeth. It would be like saying, what bands are like Yes? What the hell could *possibly* be compared to Yes? (I'm assuming the reader is aware that Yes were the most proficient prog group ever).
Opeth is like an orchid that grew out of a pile of shit. I'm sure there are tonnes of great death metal bands out there but none I've heard can hold a candle to the eternal beauty and majesty that is Opeth and it's simply not fair to them to compare them to Opeth, they should be judged on their own merits cuz relative to Opeth just about everything is crappy. Opeth has substantially raised the bar for prog metal (and I don't mean that cheesy wanker dream theatre shit, I mean *real* metal).
Anyway, my advice to those who hope to find other bands like Opeth is: don't get your hopes up, and also, if you find one anywhere near as great, tell me about it!
Mikael is a fucking GOD. Hail Opeth!
Satori