Dr Zakir Naik does not have any monopoly over the Dawaa'h but his sincerity and hard work is unmatched. He has devoted his whole life to this cause and has really become a 'voice of Islam' in the educated masses.For all these efforts , he should be applauded irrespective of whatever minor issues we have with his theology. Tablighi Jamaa't is doing a great job as well but thats more like a reformatory campaign than a well structured dawaa'h. Though i might be wrong in this assumption as i am unaware of their work outside Pakistan and UAE.