My perfect WW2 game, which may be asking for a little too much with current technology, would be a RTS style game in the same vein as the Total War series. Basically, a combination of the Hearts of Iron series and the Company of Heroes series.
You can choose whichever country on the planet you want on the campaign map, control your nations industry and manpower and direct your nation in whatever goals you want. You can pick Germany, blitz across Europe and attempt a full-on invasion of the UK, Turkey and attempt to reform the once mighty Ottoman Empire, or even small Brazil and use the global distractions of WW2 to turn Brazil into a mighty world power, maybe even eventually contending with the USA to the north. HoI does all of this brilliantly.
But when it comes to individual battles and conquering provinces on your way across Europe, you can't just rely on having on having the bigger numbers and luckier dicerolls. As your divisions roll across the border you're warped into a smaller scale battle arena, where you control individual tanks and infantry squads and so on, chosen, built and put together by you on the campaign screen, and are forced to utilize tactics and have a direct influence on how the battle ensues. Basically like Company of Heroes.
Honestly a mash up of Hearts of Iron and Company of Heroes would be my most favorite game in the world. Basically i would like a WW2 game that is truly global in every sense of the word.
Modern FPS iterations of the old classics would be cool; d-day, stalingrad and so on. But it's the what-ifs scenarios that really capture my imagination.
Edit: a word