Cars are adopting things like phased valve timing and direct injection, both of which can increase torque and HP while increasing MPG. They have also gone to more transmission gears + higher final gearing and some very lean mixtures at cruise. As an example, I have an '07 Corvette Z06 with 505 HP that gets 28 mpg on the highway. A 1967 Corvette 427 c.i. would be lucky to get half that or about 14 mpg on the same highway trip. Autos have made a lot of progress in 40 years.
Motorcycle efficiency hasn't improved as much since the 1960s like cars have. I think motorcycles eventually will adopt technologies that will increase the MPGs without sacrificing performance.