Why won't the bulbs light up brightly in my European chandelier?
If your bulbs ARE 120 volt and some are half lit then some are wired wrong.

They will be in series not in parallel.

To test this switch the light on and remove one bulb that is 1/2 lit. Another will go off- they are in series. Maybe even 2 will go off. They need to be re-wired in parallel.