Fire is the most important invention because fire help people when weather is bad, fire is hot its' his main trademark because of that it is possible to warm itself up and to prepare the food.
In my honest opinion invention of wheel is the most important invention ever because it gave birth to what is known nowadays as cars and all kinds of vehicles. Wheels let us travel around the world, transport goods faster than it used to be in the past and of course help us to get to our work faster than ever. Without wheels that are used in our cars that we use every day we won't be able to do many actions that we want to do or it would take too much time. All in all there's no such important invention as the wheel and i doubt there ever will be because with introduction of the wheel human race gained speed, what is the most important factor nowadays.