To be honest, none of the BG2 or FO2 quest bugs where bad enough to be gamebreaking
But Gothic 3 had game breaking bugs (lets not forget it also had a COMPLETELY broken sound system when it shipped, with trees and basically everything producing looping buggy sounds of hell. How that slipped through Q&A i can not even fathom.
Heck, i've personally seen
- Enemies spawn in objects, walking through the ground (literally through it), attacking from *BENEATH* the ground, Spells hitting you through solid geometry, Arrows hitting Invisible Walls in mid-air, steps up/down sometimes teleporting you to different levels (like a physic bug that bumps you up or down a floor, totally fracking weird ,p) And i even managed to fall through the world geometry, 3 times. I have seen the omnious and game-breaking bug where you couldn't clear the town with that alcohol quest, because if you already had 1 bottle the quest wouldn't give you a 2nd one (which you needed to gain popularity)
You know, i can't even remember a game that was a buggy as Gothic 3, with the Exception of that Troika Vampires nightmare.