It's very difficult to say much on the subject, but I'll try and give my opinion.

One of the reasons, I'd say, is purely because it was just more recent.

Another is the similarities in many ways to warfare today, though today's warfare has become even more sophisticated. Things like firebombing, air power, tanks, and so on were a lot more influential (at least, to my knowledge) in WWII than WWI.

Another is the genocidal aspect of WWII. The systematic mass-murder by Axis powers, and the effects on other countries (US interning Japanese, for example), and the way that the Allies chose to de-Nazify and re-educate the Germans en masse were new.

WWII created far more precedents in international law, including leading to the codification more clearly of crimes against humanity, war crimes, wars of aggression being illegal, etc.

WWII created an impetus for organizations that still stand today (unlike the League of Nations) that are more widely recognized as important in international affairs, like the UN.

WWII was a pretty big jump for the US into prominence as a world power, and was somewhat a foundation for US and USSR policy for the next roughly 50-60 years of Cold War antics.

It was the first war in which the atomic bomb was used (and the last) and signaled an age of Atomic industry unlike anything developed in WWI to that level of destructive capability.

And lastly, it's a lot easier to make things like movies, propaganda, and history about something as clear-cut as the Nazis, the Rape of Nanking, Pearl Harbor, etc. than it is about the Schlieffen Plan, to put it that way.

Arguably, WWI and WWII may be viewed as different chapters in the same war. Just as Empire Strikes Back is more well regarded than A New Hope, so does WWII seem more interesting to the modern reader. WWII was bigger, faster, louder, longer, and, most importantly, final.

The reasons for WWI are manifold, but at its most rudimentary, it was a power struggle between the great European powers. Britain and France possessed vast colonial empires. The Germans too had an empire, but of considerably reduced scale; on the other hand, they had the largest population and strongest industry, and a large, well-trained army. Russia, Austria-Hungary and the Ottomans lacked overseas possessions or significant industry, but controlled huge swathes of Eastern Europe and Asia and large populations. The result of the war was the triumph of Britain and France, though only at severe cost; the reduction, but not destruction, of Germany; and the breakup of the Austro-Hungarian, Ottoman, and Russian Empires into component pieces (though the later would restructure into the Soviet Union).

Thus, while WWI had preserved the status quo, with Britain and France continuing to be the (perceived) dominant powers of the world, and Germany, Italy and Japan in competition for the title, WWII shattered it. All of the original participants were diminished in some way. Germany was emasculated and partitioned, Japan demilitarized, Italy shattered and occupied, Poland and Czechoslovakia virtually amalgamated into the Soviet Union. Britain and France, though de jure victorious, were irreversibly weakened, their colonial empires doomed, and came out of the war battered, indebted, and no longer world powers. That had shifted to the United States, Soviet Union, and, increasingly, China.