I believe they were the first crashes, although the DC10 came close to a loss in 1972, in the Windsor incident (near Buffalo) in a situation very similar to the THY DC10.
The LH 747 was not the first loss, although it was the first crash. JAL and Pan Am both lost 747s in terrorist related incidents in 1970.
It soon became clear that the 747 incident was pilot error and the death toll was not especially high; it was taken very seriously, as all accidents are, but it was of course dwarfed by the THY incident. The difference really came down to the fact that the DC10 crash was due to a fault in the aircraft and the 747 incident was not, although a modification was suggested to make sure a 747 could not take off with its leading edges retracted.