I think you need to go way back to the early days to find the greatest person in aviation. Basically because the tough work was getting things going, making giant leaps at the beginning, and less the building process of later generations.
For me, the greatest of those early days was De Havilland. He had it all. The ability to design groundbreaking aircraft (including the first airliners), the commitment to be the test pilot, and the commercial and visionary nouse to persuade others of his vision and make it happen.
The consummate all rounder.