According to my experience they are not special in any way. Only difference is their central position in europe, they are The Centre. Even HRE is not equally centre, as they have only Poland in the east, and loads of rebels behind Polish, and Polish are so easy to wipe out, whereas France will see tough resistance in all directions.
Then again, they have massive income, and generally good troops. Good troops- able to afford them = mighty nation.

Like I said, only thing you're doing wron is that you're not aggressive enough.