Your missing a bunch of things like gearing, weight etc. That's what produces the numbers. You like to compare things but you need to know what matters in the comparison as well.
1.4l making 140 hp is 10 hp per .1 liter. How many engines are doing that? I know a lot of turbo direct injection engine doing better. But seriously.
Also with safety requirements etc going into new cars the added weight with every generation makes getting better numbers hard, besides that EPA ratings are a joke. You have people here doing muck better an much less, getting the drive they want out of them.