The main reason why LEDs are so efficient is thanks to their ability to convert most of the electricity used into visible light rather than heat.
With incandescent bulbs only 10% (at best) of power is converted into light, the rest is converted into heat. An 8W LED bulb actually produces as much light as a 65W incandescent one.
When looking at energy efficiency, not only do you need to take into account the energy savings associated with using an LED but also the savings in the energy used in the production of the components as well as that used in disposal. LEDs last so much longer than other light sources therefore fewer need to be produced or disposed of.