Well, when I understand all of you correctly the best open world game was Gothic 1.
The area is surrounded by a magical barrier that kills everyone who wants to leave and the main story is to escape this place.
I really liked the general concept of Gothic1+2.
You could go almost everywhere you want, but in the beginning you were very weak and everything could kill you.
You could also climb and swim almost everywhere, only the magic barrier stopped you.
Those games were great, just the combat system and controls were far from perfect.
In that sense BG1 was better than BG2.
BG1 was one giant map ( plus indoor areas and dungeons ) and nothing but strong monsters stopped you from going everywhere.

Prof. Dr. Dr. Mad S. Tist

World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already