I have a 1992 Honda Civic. My drivers side headlight is significantly dimmer
 

than the passenger side. Why? I am certain that the problem is not the bulb, seeing as how I have replaced both of them and switched them.I can't seem to find where the ground is...

the ground wire from the bulb is loose or rusted

This usually happens when the main beam filament burns out and only the parking lamp filament is working. That is, if the parking lamp bulb is incorporated into the main headlight, and is not separate.In your case, that does not seem to be the problem, since you have replaced, and switched them. Probably an electrical fault, like a short or disconnected wire. Have it checked out by a vehicle electrician.