You'll never beat bicycles with that metric. Passenger miles per hour per gallon might be a more appropriate metric. (I interpret "gallon" as a unit of energy: not everything runs on gallons )
So? Bicycles are very efficient. So are trains. That either do better than aviation or passenger cars does not make passenger miles/gallon (or PM/joule) a poor metric; it may mean that the transport system is not completely rationalized. Probably the least efficient mode of transport is private automobile, a mode that seems to be insanely (used advisedly) popular.
Information about American English usage here and here. Floating point issues? Please read this before posting.