LAB, you are correct. I was not implying that Helfgott is in the same league, only mentioning chazzanim whose work I enjoy. Yossele Rosenblatt is my favorite, and I have discovered that the main reason for that is that my father O”H greatly admired his nusach and was always strongly influenced by him. The first time I heard a record by YR, I thought it WAS my father singing. Their voices were very close, with Yossele’s being ever so slightly higher-pitched.
As to Moshe Koussevitsky – I have to disagree with you. Perhaps this was when he was a little older and not so well, and even then he could knock it out of the park. In his prime, he was in one sense like Pavarotti (not comparing the two), effortlessly reaching notes and trills that others could only achieve with great effort, if at all.