The candidates for me are Honda Accord, Nissan Altima, Mazda 6, Ford C-Max Hybrid and Ford C-Max Plug-in Electric Vehicle (PEV) (notwithstanding what I just said about the My Touch system in Fords), the GM Volt, and Toyota's Camry and Prius hybrids.
Taxes included here in Canada, here are how these cars stack up in terms of cost and real-world mileage numbers (from Consumer Reports road tests):
If you want the best fuel economy, nothing beats the electrics. But you have to pay $50k to get one. Is it worth it? Not at $5/gal in Canada. In the 40 mpg space, Prius V is a great choice but, again, the fuel savings over ten years barely pay for the extra cost. In the 30 mpg range, the remaining Japanese cars are all great contenders, so it comes down to the other S factors.
My overall choice is the Honda Accord 4 cylinder with CVT transmission. It has the best overall balance among the 7 S's. I especially like its simple controls for their clarity and ease of use. The whole car makes sense and gets a big high-five for Sensible.