For me Keegan was the talisman who transformed us from relatively successful side into the top team in Europe and began our 17 season domination of the English league. Fowler and Owen were merely brilliant.
Once again this really depends on whether one zeroes in on at what the player brought to the table as an individual, or looks at his playing history. I stand by the former because the latter also depends on many other factors and many other people.
Having seen Keegan live a few times I rate him very highly indeed and he was definitely pivotal in our ascent to the top, but he'd tell you himself that he did it by making the absolute best of what he had, rather than by having brilliant individual skills from the get-go. Owen and especially Fowler had a touch of magic about them that Keegan would never claim for himself..