I have lived and worked in most of the Gulf states and would list them in the following order. Worst first.
Kuwait
UAE
Bahrain, Qatar
Oman
Have not been to Saudi; DO NOT WANT TO GO!
So to answer RU's original question, I would rate Oman as probably the best of the gulf states for general driving standards.
Maybe that could be the 'least worst', if that makes any sense.
A couple of quotes from the unofficial Kuwaiti highway code I remember from my days there.
1) Do not drive too close to the car behind you.
2) Do not stop at a red traffic light until the car in front of you stops.
There were many more such gems. The problem was they were so true!