Scott going by the numbers, while the new Boeing 747-8 is slightly longer than the Airbus A380-800, at 76.25 meters compared to the A380-800’s length of 73 meters, the A380-800 is still taller, has a larger wingspan and has a higher maximum take off weight.
However … neither the Boeing 747-8 nor Airbus A380-800 are the largest commercial aircraft presently flying through the skies. The largest commercial aircraft in operation is in fact the massive Antonov AN-225 Mriya.
The AN-225, which entered service in December 1988, is very distinctive with six engines, three per wing and two tails. The AN-225s fuselage length is a mind blowing 84 meters, its wing span is 88.4 meters, its cargo capacity can swallow up a massive 46,000 cubic feet of cargo and its maximum take off weight is an unbelievable 1,323,000 pounds!
By comparison, the Boeing 747-8F can hold 30,177 cubic feet of cargo with a maximum take off weight of 975,000 pounds. The Airbus A380-800F can hold 40,000 cubic feet of cargo with a maximum take off weight of 1,200,000 pounds.
It should be noted that Airbus has not produced a cargo version of the Airbus A380 at this time and has no cargo customers on the books for an A380-800F. The current Boeing 747-8 aircraft undergoing tests for certification are all cargo aircraft, the 747-8F. There is presently only a single AN-225 in service and it is cargo only. These three aircraft however are the three largest commercial aircraft currently flying and the design of the AN-225 makes it uniquely capable of loading massive items in a way the Airbus A380F would not be able to, should Airbus source cargo variant customers.
Below is a compassion graphic of the 747-400, A380-800 and AN-225 that was supplied to me by Antonov a while back.
Hope this answered your question!