The 747 had to and could grow over several engine generations to become some success as the 747-200 (mostly used for range) and big success as the 747-400 (perfectly paired with the 767 back then).
The A380 was meant to become a family of aircraft. It's like the A319 member of the A320 family. Closing the program after only one version and generation now is a bit of a change of mind. Where is the stamina Boeing had with the 747?