World's best Civil aircraft to me is the one which is both passenger & airline friendly. Passenger terms involves safety, security, comfort and accessibility. Airline friendly depends on operating cost, maintenance cost, ability to train crews
& pilots easily and impart them. In all these aspects Airbus A320 does a good job. Its the first airline which really redefined the civil air travel by its technology, performance. Some of the notable things are the introduction of side stick, winglets, eifficient CFM engine, digital fly by wire & FADEC. Like Rolls royce for cars, airbus is for aerospace. Apart from this its the aircraft with modern cockpit(commonality), 1st in single aisle family.
Airbus sets a benchmark in aerospace industry by incorporating the highest levels of automation with safety *** security in its aircraft. Not only that a A320 pilot can upgrade to A340/A380 easily.
So my vote goes to Airbus 320, the queen of skies & the airbus the emperor of air.