Do you consider the first two Opeth albums Gothenburg?

I slightly prefer Bergtatt over Nattens Madrigal, but it really depends on my mood. NM is the dirtiest, sickest, most disgusting album I've ever heard, but if anybody can not feel elation at that main riff in Wolf and Fear, they have a problem.
I'm also glad they've evolved. I really enjoy Themes From... etc, and I'm getting into the new one as well.

NM is jollyfolk compared with a lot of albums i've heard
 
Definitely not gothenburg, but ATG-With Fear... album features some awesome 2 guitar parts that aren't just 3rd, 4ths 5ths... See the song Primal Breath. That ATG album was a lot more "Death metal" as Opeth's first two seem more Lute inspired Black/Folk Metal. Definitely some celtic rhytms
 
No, I wouldn't call it Göteborg. To me, that's the first couple of In Flmaes, Dark Tranquility and At the Gates, mainly. Basically, a mix of Heavy Metal like Maiden, and Death Metal.
Opeth doesn't quite fit in there.

By the way, speaking of old Opeth, does anyone know/like the first Ulver : Bergtatt?
I just love the atmosphere and sound of that recording. Very folk-ish, too, but rooted in Black Metal. I wish Ulver were still like that.
You'll find a fair few Ulver fans here. As much as Bergtatt is incredible, I don't in the slightest miss their bm/folk origins. As long as they keep making masterpiece after masterpiece I'm happy, no matter what style it is in. Plus although they don't stay in a style long enough to destroy an entire genre, given how short a time they spend in a style its fairly incredible they can create something up there with bands who have been gradually perfecting it for years.
 
Clearly there are differences, like Opeth's longer songs, different take on the twin guitar harmony, etc.

But if you listen to In Flames "The Jester Race/Black-Ash Inheritance" from 1996 and then Orchid or Morningrise, there are definitely similarities. The sudden switches between death metal and acoustic passages, the twin guitar harmony over growled vocals... generally seem to be coming from very similar influences, even if Opeth is more progressive and In Flames does more traditional song structures and straightforward riffs/thrashing.

Listen to "Moonshield" or "Lord Hypnos" or something and then "In Mist She Was Standing" or "The Apostle In Triumph" and its hard not to see some similarities.
 
...that's the first couple of In Flmaes, Dark Tranquility and At the Gates, mainly.

By the way, speaking of old Opeth, does anyone know/like the first Ulver : Bergtatt?
I just love the atmosphere and sound of that recording. Very folk-ish, too, but rooted in Black Metal. I wish Ulver were still like that.

Everybody's saying that those 3 bands pioneered Gothenberg, but has anyone ever heard Sentenced's "North from Here"? A very underrated melodeath album.

And yeah, Bergtatt is a great album. It's one of my favourite atmospheres for any recorded album. It would be great if they still did folk/black metal, I love that style of music. Then again, I really like "Shadows of the Sun" as well...