With 4 kids a closet is the only safe place to keep most of my stash. The 3 youngest don't even know what's in it. It is has a bolt lock high up on the door to keep out prying eyes.
I allow all the kids access to the 360, WII, Xbox, and PS2 games.
The 2600, 5200, 7800, NES, SNES, N64, and all loose carts are kept in drawers in the game room, but the kids pay no attention to them.