from what point of view is the right headlamp brighter than the left - when you are in the driver's seat or when you are in front of the car looking at the headlamps?
if your point of view is from the front of the car, and the headlamp to your right (i.e., the left headlamp of the car) seems brighter, then my guess is that you have euro-style headlamps, which have asymmetric lowbeams.
when you project your lights on a wall (i.e., from the driver's perspective), each projected lowbeam has a sharp horizontal cutoff that bends up at an angle as you move to the right of the projected beam on the wall (for cars designed to be driven on the left side of the road, the pattern will be reversed).
The part of the beam that has a horizontal cutoff is is designed to brightly illuminate the left side of the road without blinding oncoming drivers (if properly aimed), and the part of the beam that is angled upwards is designed for illuminating roadsigns and other stuff on the right side of the road.
if you were standing in front of the car looking back at the headlamps, my guess is that your eyes were in the upswept part of the car's left lowbeam (i.e., the headlamp to your right), making it seem brighter than the other one.