Fisk is undoubtedly a major figure in Spidey-lore; I always feel hesitant branding him as a "top villain" simply because I could never really buy the mano a mano fight scenes in which Fisk hung in there with him. There were numerous such scenes throughout the Lee/Romita era and then again throughout the '70's culminating in the story in which Fisk defeats Spidey and is about to finish him off when Vanessa gives him the ultimatum of finishing him off or leaving with her (circa ASM#197 or so). Re-reading those tales now require a huge suspension of disbelief; the really early tales one could say Fisk took him by surprise, the old "he may look fat but it's all muscle" line but, after that, Spidey should have mopped the floor with him every time as he did in "Back In Black". Having said that, Fisk works really well as the King of NY; the complex figure who sometimes helps Spidey when it furthers his own interests, the shadowy overlord who is always 4 steps ahead of everybody else. In that regard, he is one of the book's best characters and always will be.