Is TOEFL the most required language test?

TOEFL is considered to be the best measure for English language proficiency in the world, its comprehensive format highly detects the taker's level, however recently more and more admission offices such as those in universities and educational institutes are using the IELTS exam.

What if you have a Cambridge Advanced certificate in English.
Is it recognised in the gulf countries?

No, IELTS is the most required language test.