This is something I've always wondered, as it surely couldn't have been widely anticipated, at the outbreak of WW2 in Europe in 1939, that the coming conflict would end up eclipsing WW1, particularly given how deleterious an impact that war had already had in the not-then-too-distant past. I've always wondered when the idea first started to be seriously circulated in various places and arenas that the war they were engaged in was going to end up being even bigger - more destructive, more lethal, more widespread, etc - than the previous one. My presumption is that this realisation has to have happened during the war, rather than after it - one could hardly fail to grasp quite how mammoth a conflict was going on, circa 1943 for example.
In many countries in Europe the first world war is still referred to as 'the great war', la grande guerre. In France for example there was barely any fighting most of the war, quick occupation and no renewed fighting until D-Day, while the first war saw years of continuous fighting on French soil.
The difference in scope lies in the global scale of the fighting. The first world war was essentially a European one that included their colonies to a limited extent, it was a world war but not as much as the second world war which had a whole second theater, the Pacific.
I know I'm not answering your question but I'm trying to shed light on the different perceptions people in different countries would have of these conflicts. And the different nature of the conflicts and the different effects on different countries means that for some countries the 1st world war is still the great war, while in others it is overshadowed by the second.