Pretty easy.
Sun Tzu.
He influenced some of the greatest generals through The Art of War. Napoleon. Mao. Vo Nuygen Gap. Ho Chi Minh. No general has ever achieved such a legacy.
For contemporaries, though, Patton and Zhukov are right up there. I also like Rommel as well, but he was given a very raw deal in WW2.
Back from the dead, I'm afraid.