TLDR: Electric vehicles get way more miles per unit of energy, but not per unit of mass/volume of energy storage.

Internal combustion engines are fundamentally pretty inefficient-only about 30% of the energy they use goes to actually moving the car forward. This is related to how energy is extracted from the gasoline (research Carnot efficiency if you want to know more about the theory of how heat engines like we have in our cars work). The reason we can still make practical cars this way is that gasoline has a lot of energy packed into a relatively small mass/volume.

Electric motors have much higher efficiencies-around 90% of the energy they use goes to moving the car forward. However, the range is limited by the capacity of the battery, and the energy to mass/volume ratio for a battery is way less good than gasoline. We've only gotten the battery technology good enough to compete with gasoline on range relatively recently (especially if you consider the difference in recharge vs refill time).