It is possible to replace a halogen headlight with an ordinary headlight, but only if the halogen headlamp is a sealed beam. Halogen headlights with interchangeable bulbs only accept halogen bulbs. There is a trade-off to consider; ordinary sealed beam headlights cost less than halogen sealed beams, but they are not as bright.
Halogen lights are about 40% brighter than conventional incandescent lights. Light output is measured in units called lumens, which is a more accurate measure than candlepower. Conventional incandescent bulbs give off 15 to 18 lumens per watt. Halogens produce 20 to 25 lumens per watt, extending average headlight range 200 feet further down the road. Halogen light is whiter, which also aids visibility.
The filament in a halogen bulb is thinner and burns hotter. They are called halogen bulbs because of the gas mixture used to fill the glass; halogen plus krypton, argon and/or nitrogen. The gas mixture conducts heat away from the filament to prevent it from burning out. Halogen helps redeposit microscopic particles of tungsten that boil off the filament back onto the filament. This extends filament life and prevents bulb darkening with age.