Id say its due in a large part to Tony's false fingertips and the aspects Tony has had to utilize on his guitar (String gauge etc.) to compensate for that. But aside from that he's a true original. Players like Rhoads, Blackmore, Michael Shenker, Van Halen, Vai, Vaughan, and Iommi inspire, but are impossible to copy 100%. They play with nuance and most importantly they play with tons of feel. Its easy to copy notes & play them in the same order as their heroes, but not easy to copy or emulate actual feel.