Opeth, like any band, have their strengths and their weaknesses. There are other bands out there that will be better than them at some things, while being worse at others. If you want a band as good as Opeth you'll find plenty, if you want a band exactly like Opeth you won't find any. The reason is that once you get to a level of songwriting and playing ability to write songs like Opeth, you will have already developed your own style (just like opeth did, mixing together all their influences).
And thats what we see here, all the bands mentioned here have similarities to Opeth, but they also have differences. Some of the are directly influenced by Opeth, and you can hear it in thier music, but they still have pretty big differences. It doesnt mean nobody else is good enough to write music like Opeth, it means they aren't trying to.
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Uhh, you could check out my song "Forestall", has quite a few similarities. www.mp3.com/dave_caswell