Blade Runner was about so much more than Deckard. Of course SW 4-6 was about much more than Han Solo, but that character was so vital to the story, and Ford gave him life that will endear Solo to fans for generations to come. And of course Indiana Jones is Indiana Jones.
Roger Ebert wrote a neat thing about Ford. "In a scene where everything is happening at once, he knows that nothing unnecessary need be happening on his face, in his voice, or to his character. He is the fulcrum, not the lever." He is the human element amid all the cgi, effects, green screens and explosions; his portrayals are what we the audience identify with and keep the story grounded despite whatever else might be happening on the screen, and that is why he is one of the greatest film actors of all time.