Engine efficiency refers to the percentage of energy lost when converting stored energy into kinetic energy. No engine creates energy (it's one of the basic laws in physics: energy cannot be created or destroyed), so discussing how much energy an engine creates doesn't really serve to validate or invalidate any engine, gas or electric.

Comparing today's typical efficiency of consumer gas engines and consumer electric engines puts electric vehicles significantly ahead: gas car engines operate at 20% efficiency, whereas electric car engines operate at 60% efficiency. And the electric vehicle industry is still young, so we will likely see significant improvements in both energy storage and thermal efficiency.

I suspect improving battery weight is at the top of every EV manufacturer's list of desired improvements. Right now the energy density of a lithium ion battery is around 0.7 MJ/kg, whereas gasoline stores around 44 MJ/kg. There's quite a bit of research going on around increasing efficiency of electricity storage, so I suspect that will improve significantly within the next 5 to 10 years. Increasing the energy density of EV batteries from 0.7 MJ/kg to 2.8 MJ/kg will effectively make electric batteries lighter than most car engines (and would also increase the single charge range into thousands of miles).The future looks pretty exciting.