An apples to apples comparison is going to be nearly impossible to find. But look at this link,
Compare Side-by-Side
At cruise, a car doesn't need much power at all compared to how much power it needs during acceleration, particularly if the vehicle can't feel underpowered. So what has to happen, and what we're finally seing automakers doing, is producing smaller displacement/high(er) boost engines. This combination produces power comparable to a larger displacement engine but much lower fuel consumption while cruising because the vehicle does not require the power.
If you want to turbocharge a vx engine you're going to increase fuel consumption. If you instead get an engine half its size and increase compression, add direct injection, add a turbo, properly tune it, and add a lower gear ratio top gear, you may very well improve efficiency.