Rav Hershel Schachter is a gadol par excellence. I believe YU is the citadel of torah b’zman hazeh. R’ Rakeffet is a gadol in the shutim; I have learned thousands of responsa by listening to his shiurim. R’ Simon, R’ Rosensweig, R’ Aryeh Lebowitz, R’ Shalom Rosner, and many others are gedolim b’torah.
I also like the shiurim of Rabbi Zweig from Miami, Rabbi Betzalel Rudinsky, Rabbi Yosef Berger from Baltimore, Rabbi Yoseph Radner, Rabbi Immanuel Bernstein, and Rabbi Yissocher Frand.