I am torn between 2016 and 1990, and ultimately choose 1990. There was a wide variety of cool stuff: highly-engineered quality luxury cars (LS400, E32, Town Car, XM, introduced Mercedes W140), cheap offroaders, like the Samurai or Feroza, cheap performance machines like the C4 Corvette or Mk2 MR2, high-end super/hypercar experiments like the F40, XJR15 or Cizeta-Moroder V16T, or just plain well-engineered ordinary cars by the likes of Honda, Volkswagen Group or Mercedes-Benz.
1967 In a land before federal emissions regulations, and just after PCV regulations, came 1967. It was the year Carroll Shelby divorced Ford, Lamborghini was making the first mid-engined "supercar," we had 300+HP muscle cars, beautiful 3 liter Formula cars. In Europe, there were cars like the Jaguar E-Type, Porsche 911 Targa, Maserati Ghibli. The Ferrari 288 GTO was a gleam in an engineer's eye, and the Maserati Merak and Bora were around the corner. In Japan, Toyota were making the 2000 GT. Honda were busy releasing the cute little N600 into the world. That car would go on to birth the Civic in 1972. Nissan were making the Nissan Sports, which would go on to be replaced by the Fairlady Z. Ford had just released the Shelby GT500, Dodge redesigned the Charger, and General Motors released the Chevrolet Camaro. In 1966, we chose to go to the moon not because it was easy, but because it was hard. In 1967, The United States shot Apollo 1 into low Earth orbit. Modern day cars are better. They're more comfortable, faster, safer, and more polar bear friendly. They'll brake for you, steer for you, and let you see what's behind you. Unfortunately, they're also all on Prozac.