The EAA shares that the definition of service ceiling is the height above sea level at which an aircraft with normal-rated load “is unable to climb faster than 100 feet per minute under standard air conditions.” //

Boeing 747
Lufthansa previously bragged that its 747-400 could reach the highest altitude in its fleet, reaching a max altitude of 44,947 ft (13,610 m). Meanwhile, the modern 747-8, which is well deployed by the carrier, has a service ceiling of 43,100 ft (13,137 m). //

Boeing 767
Including extended ranges, the 767 family has six variants. These planes have a service ceiling that ranges from 43,000 (13,106 m) to 43,199 (13,167 m). //

Altogether, the surface ceiling figures of most of the modern jets are not so far apart. Regardless, the widebodies generally have a higher ceiling than the narrowbodies. However, there was a clear winner earlier this century when Concorde was around. This supersonic jet had a whopping service ceiling of 60,000 ft (18,300 m).