An RTS game with:
realistic scale (the soldiers are as big as the tanks! the war factories are slightly bigger than the tanks! forget that stuff.)
INSANE customization (down to every nut, bolt, pipe, just about anything ever - basically a vehicle/structure editor in which you can edit absolutely anything)
modular buildings (a barracks isn't just the barracks - you also have to have training grounds, armories, etc)
physics, not underdone (you just hit a building with a nuclear bomb! a few pieces break off.(I'm looking at you, C&C tiberium wars)) and not overdone (the tank exploded, throwing itself, somehow, five hundred meters into the air!(I'm looking at you C&C Generals)) - basically dynamic physics rather than some pre-scripted booms and bangs.
large maps, the size of whole cities - nay, counties
persistent debris - that thousand meters across building you just destroyed didn't just disappear!