Ethanol is not a viable alternative to oil-based fuels because it does not produce as much energy per gallon as gasoline.  The corn-based ethanol being produced domestically actually takes more energy to produce and transport than the energy it contains.  Ethanol is also not logistically feasable for a nation the size of the United States.

The most promising alternative energy source appears to be the hydrogen fuel cell.  It is a proven technology, albeit an expensive one.  At present, it is a cost-prohibitive proposition, but will become less so in future.  Until then, oil is about the only thing that produces the quantities of energy necessary to power the engine of our economy.