Sort of. One of the major design elements of a real hybrid is that it uses a smaller, more efficient gas engine. That's what the electric motor is really there for -- the gas engine can't provide enough power on its own for proper acceleration under many circumstances, but the two motors combined can. So the electric motor is the thing that enables you to have a small, efficient gas engine, and the regenerative braking is just a good power source for the electric motor. On the highway, the hybrid has to carry around the weight of the electric system, but it carries less engine weight and still benefits from using a small engine.
In practice, for me at least, I get 45 mpg highway out of a Prius, which is pretty decent.