Hyundai's Genesis sedan is much improved for 2012, yet its position in the market won't change one bit. The Genesis will continue to give engineers and product planners at Mercedes-Benz and Lexus fits, thanks to the sedan's upgraded V-6 engine, revised suspension tuning, and a new eight-speed automatic transmission -- not to mention the 429-horsepower R-Spec model.Hyundai expects highway fuel