World War II is easy to make a game about. Everyone knows Nazis suck. A World War I game, done properly, would require some deep treatment of the tragic meaninglessness of the war rather than just being an all-out arcadish shooter. It'd be really cool to see a time-traveling RPG where you have to try to prevent WWI in order to also prevent WWII and the Cold War. How come no one ever makes time-traveling RPGs set in the early 20th century, seriously? That would be fun.
Bowser does look rather ox-like now that I think about it. I'll count it as a loss.