If you want to tell the story of ww2 as some of you suggest, from any side, and get more involved with the events that went on and what happened and why, then you pretty much need to get away from the fps scene and go towards RPG or an RPG/FPS type game, which I don't think has been done before, or at least not done well enough to be remembered.
If you're still looking for the next big fps though WW1 is probably the most likely place. If you're talking about german perspective then you can take notes from the famous 'All quite on the western front' which was actually originally written from the german perspective, and from the perspective of a school aged boy that thought it would be great to leave school and join the Army with all of his class mates. Though as the story progresses one by one he looses his class mates, as the reality of it all sinks in. Interesting it was quite an outragous anit-war story in it's time and was one of the many books Hitler had burnt when he came to power.
And point to note, yes the ww2 shooter has been played out. It replaced the whole US vs Russia genre that was flogged like a dead horse in it's time. As for the Russian perspective it's interesting to note that more Russian people died in the city of Lenningrad than the entire combined Allied (British/Americian) losses for the war. They got to the point where they had to boil down shoes/boots so they could eat the leather. It puts D-day in perspective.
There was an old Documentary series from back in the 70's called "World at war" that covered every indivdual theatre from the fall of the Cech republic to bush fighting in Burma, Italy, the U Boats, the mass bombing, why the US stayed out of the war as long as it did, and all of the places inbetween, and told by the people that actually experienced the events, including the german people. I'd definetly recommend it to anyone who can get their hands on it.
Lastly, I want to see another game like an old favorite I used to play called Conflict: Europe. The game perspective was taken from the war room, where you moved armies around, and resupplied units and generally told them where to fight. It was all about the Macro-management. You could assign air squadrans to various roles like strategic (read civilian) bombing or Air superiority, Interdiction, and had access to a wide range of nuclear options if you wanted to go that way. It was a brillant game and I've never seen anything done like it since. And a newsfeed would come up each day of indivdual events that had happened based roughtly on how you were doing overall.