My vote for the greatest aircraft ever is for one not nominated: The versatile Consolidated PBY “Catalina” flying boat.
The tool, the servant, the magic carpet, the seven league boat. A graceful form expressing its function. In service from the tropics to the arctic, on land and sea. Performing key roles in war and peace unsung and unrecognized. Its mission and its job done out of sight and now forgotten. Sad. Ask the men who crewed the PBYs.