As Mitlov said, the term 'Best Engineered' can be taken in many different ways. So I have picked five cars based on 5 categories:
Best Practical Engineering - The Honda Fit - For such a small car, it is crazy how much room you get inside. And although the rear seats may not be the most comfortable, the fold into the floor option allows way more hatch space then that car should have. Add to that great handling and good fuel economy.
Best 'Unconvential' Engineering - The Chevrolet Corvette - A pushrod Motor, Sideways mounted Leaf Springs, Fibre Glass Body. This car using 1960's technology can outrun most sports cars (supercars?) today and is reasonably priced to boot.
Best 'We Did it Cause We F'n Can' Engineering - The Mazda RX-8 - Say what you will about the Rotary, but this car is still one of the most fun to drive cars on the planet. It has perfect balace, a great shape and ridiculous responses. And unlike a S2000 or Elise, it also seats four and can be used day to day without (too many) issues.
Best Technological Engineering- TIE- Nissan GT-R and Porsche 911 Turbo S - Different spectrums of pricing, but same idea. Make anyone look like a hero at the track driving these cars. Is more like driving a video game then a car? Maybe, but it is one fast video game.
Best Wolf in Sheeps Clothing Technology - Nissan Juke - Styled like an ugly duckling to some, for $20 000 you get torque vectoring AWD and a 1.6L turbo motor putting out 117HP/L.