Since I don't really know much 1.6 engines, and I will NOT nominate the Nissan Versa, my choice for this Best "X" Litre engine is the Ford Fiesta ST's 1.6 Turbo

This little engine is pretty much a Chihuahua dog. Small, Barky, Angry, and packing much more of an attitude than bigger engines. This 197HP and 202 lb Ft. mill is one of the main ingredients that transforms an already fun and quirky hatchback in a Grinning factory. Only drawback, sound symposer.