Well, a car headlight will have a certain amount of lumens produced but that's not what you see. What you actually see its the brightness of that light (lux) which basically is the intensity of light relative to the projected area from a surface. Its a bit weird to explain because even if you read the classic definitions they all seem the same thing. To put it in practice lets say you are in a garage with dimmable lights, you turn ambient light down and turn on your headlights, then you slowly raise the room light and the beam that was visible in the dark at one point slowly disappears. The headlight is still producing the same amount of lumens but for your eye it will be harder to perceive its illuminance because its being drowned by the ambient light. Now if you were to fit one headlight with the OsramOriginal and one with the NightBreaker, theory says that you should be able to distinguish the latter even when the ambient light has drowned the first because of an higher lux.
The color has is impact too as a "whiter" bulb will give more lux.
I left a picture from the net just for some visual comparison between beam of different lights. Another I had in the answer I deleted as it seemed to me just a marketing doctored image, like a lot of the images I considered, others would have been a pain to add here. What I was looking for was an actual controlled test of a few different bulbs with proper measurements, maybe from an automotive magazine, but up to now I have not found it. The closest I found is this http://www.which.co.uk/cars/driving/sat-navs-and-car-accessories/best-car-headlight-bulbs/ but while they mention how the test was performed it appears they publish the results but not the measurements proper which would be the actual useful part.
Before deciding to go with a brighter bulb one should first check that the light beam is projected where is useful and that the existing bulb isn't old and tired and that the headlight glass isn't all oxidized and fogged up. So users reviews often are a bit of a hit and miss as indication if you don't know how they were driving before.
Personally I always have the impression that with the brighter bulbs I can see less of whats outside the light beam and I don't like them. Others I know instead have as much light as a spaceship in front of them and would still go brighter if they could.
A word on regulations: if you look at how an headlight is designed not all the light is directed towards the road, the whole beam is designed so a certain percentage of light is thrown higher up. If a light is above limits then even the amount of light high up increases becoming dangerous for the others on the road. Headlights that were designed for Xenon bulbs for example would throw the extra on the road but the amount of light higher up is the same than the conventional lights (legal) they often have an automatic regulation of the tilt depending on the load for the same reason. In some countries you can have a car born with Xenon headlights and they are perfectly legal even if above the general Lumens indication because they are designed to throw the light in the right way and they are self-leveling, while any aftermarket kit is considered illegal. So even there Lumens don't tell the whole story. (And, beside everything, some bulbs rated at very high lumens waste so much heat that can actually damage plastic headlights apparently)
Edit, to try to explain things further:
When you measure the power of a light source you have various ways to measure the light that is emitted by it.
One way to express that is the Candela which basically is the amount of light emitted in a tridimensional area. It doesn't care about distance from the light source or how wide is the area illuminated. The angle used is a steradian which is the way solid angles are measured and in practice covers an area of 1m2 on a sphere of 1metre radius, A full sphere has an angle of 4π steradians (and at the end its just a fancy concept we don't care about since we wont have to do any calculation when buying a lightbulb)
You have the Watts that are what people is most familiar with and it was how we expressed the power of the old house light bulbs. Watts in itself mean little as it is the amount of energy required to emit a certain amount of light and now that there are different choices from the old plain household incandescent bulb, efficiency has increased so the energy used is less related to the light produced. That's why now Lumens are something we use more often.
The Lumen is the light flux a certain source emits. As such if you take a flood light and you put a reflector that narrows its beam you end bringing (reflecting) more light in a narrower cone increasing its flux instead of wasting it in directions you are not interested in. It does relate to the angle of the beam produced and as so its basically becomes a measurement of how many Candela are thrown within a certain angle and so its measured by multiplying the Candela of a light by the angle in steradians. So 1lumen = 1 candela steradian, it doesnt matter the distance its measured at.
Then you have the Luminance and the Lux, these are the measure of the light emitted, for the former, or reflected, for the latter, by a surface. Since we don't actually perceive the light moving through the air but we are aware of light as a reflection by everything that surrounds us, these are more related to the light brightness we actually see. These measurement actually take distance in account, they don't care of the angle of a cone of light or its intensity per se, If you want you can consider them as a measure of the results of all the defined above as they will indicate how illuminated the target surface is and its what changes when we say that one headlight is brighter than the other
If someone wants to spend a couple semiboring hours some more in-dept explanation can be found here: http://www.intl-lighttech.com/support/measurement-geometries-chapter-7-light-measurement-tutorial
