The driver's side light should be aimed lower than the passenger's side. It's a safety thing. That might be what you describe as the difference in brightness.
If you can stand in front of the car and notice that one light is more intense than the other, well then maybe there is a problem. But as for how far each lamp illuminates, the left will always be shorter than the right.
2009 E92 335i | 6MT | Black Sapphire | Black Dakota | Aluminum Trim | Premium | Sport | Heated Seats | PDC | iDrive | HD Radio | M-Sport Shift Knob