“Best” shiurim is all relative. It depends on the person and what kind of shiurim they need. If someone is a baal teshuva looking for inspiration, they wouldn’t gain much from a shiur by R’ Wachtfogel. A yeshiva guy might not enjoy a shiur by R’ Wallerstein.
For yeshiva guys looking for a yeshiva, there are 2 names I’ve heard from many people as far as giving the “best” shiur:
R’ Elya Ber Wachtfogel (South Fallsburg)
R’ Berel Shachar (Edison)
I know people who went to those yeshivos specifically to have them as a maggid shiur.
Personally, when I was in Darchei Torah, I loved R’ Wachsman’s shiur (although it was just for first year Beis Medrash). I’m told that R’ Altusky also gives a very good shiur, although I was never in his shiur, and can’t attest to it personally.