Well, on my 1989 300SE the rear dome light comes on with the switch as well, but with the added bonus of coming on when the rear doors are opened. The light does not come on however, when the front doors are opened alone.
I'm sorry that I don't have an answer for you, but did you try the switch that's attached to the front dome light? (if your car has one. ???)
2004 E320 Wagon
1998 Range Rover 4.0 SE