Someone on this thread wondered something similar recently (or wondered how long the WW2 obsession will last) and I've pondered it myself since
I think the rapid expansion of the global population, variety and ease of access to various kinds of media makes WW2 linger more in the collective consciousness than any other one would have. In the past with wars you would have had oral histories with stories and experienced passed down first-hand through people who actually experienced it. Maybe some literature, some limited national press and... that would be it. Since WW2 happened - and even compensating for it being the largest scale conflict ever - there have been a lot more people to experience the aftermath and pass down the personal knowledge of it, plus the endless possibilities of increasingly realistic and accurate media depictions of it in films, TV, video games, whatever.
Effectively the impact and legacy of the war was and remains more widespread than any other conflict, there have been more people involved in it still around, and there's been a much greater scope for media coverage of it and media depictions of it after the fact. That's before getting into the apparent collective national inferiority complex of The British that saw 'their' greatest triumph followed shortly by the breakup of their Empire and a continued dwindling of their global influence/relevance.
On the other hand, the 100th anniversary of the end of WW1 is the last I remember hearing about it on the news, so there may yet be hope for an end of poppy shagging. I'm sure the resident qualified historians can tell us whether what I've said makes any sense.