Well, IMO, the ultimate "plane of planes" would be the DC-3/C-47. Over 70 years after its maiden flights it's still around, carrying passengers and cargo through out the world, on a daily base. An aviation masterpiece that came out a way ahead of its time !
The second place would go to the B-707. This plane has changed the face of the commercial aviation.
The third place, IMO, would go to the B-737, the world's best selling commercial airplane.
Your list/thoughts would be appriciated !