His looks, which grows and grows on you. His intelligence, which gets reflected in his work, activities. Of course most importantly his acting, be it playing any character school boy, a romeo, a opportunist journalist, a tapori, a IPS officer, a flunky, sedha-sada taxi driver, a cool urban dude or a villager. He played every character with so much conviction. After looking at his range of good work, no other top actor of his time I can imagine replacing him.