I've got to suspect that the greatest living acoustic guitar player is some gypsy or fulani no one has ever heard of. However, if you have to pick one, Paco de Lucia is probably your best call. OTOH, they had a storry on ATC a bit ago about classical guitar, and there were a couple of folks on there who could really give him a run for his money. Sadly, I can't recall any of their names.
