It will not be easy to answer this question properly as it would be difficult to determine who is the most famous orchestral conductor. A conductor might be praised by certain people and disliked by others. This is the same with musicians, footballers and many others.
Here are some of the well known orchestral conductors: Carlos Kleiber, Claudio Abbado, Leonard Bernstein, Colin Davis, Gustavo Dudamel, Nadia Boulanger, Valery Gergier, Pierre Boulez, Simon Rattle, Herbert Von Karajan, Wilhelm Furtwangler, Arturo Toscanini and Carlo Maria Giulini.