I remember trying to play Gothic 3 on a AMD3600 with a crappy graphic card... the game looked like a buggy and slow version of Gothic 2.
One year later I did the same experiment on a AMDphenom tri-core with good graphic card... the game looked better but was still buggy and slow. = )

Exactly. Year it was relased I tried to play it on a rig which handled Oblivion very well. It was unplayable. Recently I tried to play it on my machine which is able to handle almost every modern game on high details and resolution. Still wasn't too good for Gothic 3.

Well, as I said the Community Patch 1.70 has been released, and it seems to fix a lot of the issues. I'm playing it on almost full graphics, and it runs just fine, but like I said, I had some lightning issues. I haven't played much though. Combat felt more refined (as in less of a click fest), but haven't noticed much beyond that. I also noticed in the main menu that they called it the Enhanced Edition...
EDIT:
This place needs a italics tag.

Gothic was always buggy and slow. It's like the ArmA of RPGs. Get used to it.

To be fair, he did say it's G3 that's slower than G2
I tried Gothic 2, found it to be not bad. At least it was more intriguing than Morrowind

All the Gothic series always seemed to be released half-baked, buggy, and it was like there was no attempt to fix any problems reported whatsoever... until people got mad.